Biological Psychology Notes Tutorial 1 PDF

Pinel, Biopsychology, chapter 3, pages 72- Kalat, Biological Psychology, Chapters/modules 3.1, 3.2, 1.2 Divisions of the Nervous System **Central Nervous System (CNS)** within the skull and spine - *[Brain]* is located in the skull - *[Spinal cord]* is located in the spine **Peripheral Ner...

Pinel, Biopsychology, chapter 3, pages 72- Kalat, Biological Psychology, Chapters/modules 3.1, 3.2, 1.2 Divisions of the Nervous System **Central Nervous System (CNS)** within the skull and spine - *[Brain]* is located in the skull - *[Spinal cord]* is located in the spine **Peripheral Nervous System (PNS)** division outside the skull and spine 1. **Somatic Nervous System (SNS)** interacts with external environment a. [Afferent nerves] carry sensory signals from the skin, skeletal muscles, joints, eyes, ears etc to the nervous system b. [Efferent nerves] carry motor signals from the CNS to the skeletal muscles 2. **Autonomic Nervous System (ANS)** regulates body's internal environment a. [Afferent nerves] carry [sensory signals] from internal organs to the CNS b. [Efferent nerves] carry [motor signals] from the CNS to internal organs Afferent=going towards something (the CNS) Efferent=going away from something (the CNS) i. **Sympathetic Nerves** autonomic motor nerves that project from the CNS in the *lumbar* (small of the back) and *thoracic* (chest area) regions of the spinal cord. ii. **Parasympathetic Nerves** autonomic motor nerves that project from the brain and sacral (lower back) region of the spinal cord. - **Two-stage neural paths**: they both project from the CNS and go only part of the way to the target organs before they synapse on other neurons (second-stage neurons) that carry the signals the rest of the way [sympathetic]: project from the CNS synapse on second-stage neurons at a substantial distance from their target organs [parasympathetic]: project from the CNS synapse near their target organs on very short second-stage neurons +-----------------------------------------------------------------------+ | **Clarifications** | +=======================================================================+ | 1. sympathetic nerves stimulate, organize, and mobilize energy | | resources in threatening situations, whereas parasympathetic | | nerves act to conserve energy | +-----------------------------------------------------------------------+ | 2. each autonomic target organ receives opposing sympathetic and | | parasympathetic input, and its activity is thus controlled by | | relative levels of sympathetic and parasympathetic activity | +-----------------------------------------------------------------------+ | 3. sympathetic changes are indicative of psychological arousal, | | whereas parasympathetic changes are indicative of psychological | | relaxation. | +-----------------------------------------------------------------------+ **The 12 pairs of exceptions...** **cranial nerves** - numbered in sequence from front to back A diagram of nervous system Description automatically generatedMeninges [Idea: The CNS are the most protected organs in the body. They are encased and covered by three protective membranes called meninges] 1. outer meninx **dura mater** tough membrane 2. the immediately inside dura mater **arachnoid membrane** 3. space below **subarachnoid space** - contains [large blood vessels and cerebrospinal fluid ] 4. innermost meninx delicate **pia mater** (pious mother) - [adheres to surface of CNS] **dura mater meninx** **arachnoid meninx** **pia mater meninx** Ventricles and Cerebrospinal Fluid **For the protection of the CNS** **Cerebrospinal fluid (CSF)** which fills the [subarachnoid space, the central canal of the spinal cord and the cerebral ventricles of the brain] [function]: supports cushions of the brain; those who lost it have headaches and stabbing pain when shaking the head produced by the **choroid plexuses** (network of capillaries or small blood vessels that protrude into the ventricles from the pia water) excess fluid is continuously absorbed from the subarachnoid space into large blood-filled spaces (dural sinuses) which run through the dura mater and drain into the large jugular veins of the neck. **central canal**: small central channel that runs the length of the spinal cord **cerebral ventricles**: four large internal chambers of the brain two lateral ventricles third ventricle fourth ventricle - [the subarachnoid space, central canal and cerebral ventricles are interconnected by a series of openings and thus form a single reservoir ]  **Hydrocephalus (water head)** --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- [Cause]: cerebrospinal fluid is blocked by a tumor near one of the narrow channels that link the ventricles (i.e. near the cerebral aqueduct, connecting the 3^rd^ and 4^th^ ventricles) buildup of fluid causes the walls of ventricles and entire brain to expand [Treatment]: draining excess fluid from the ventricles and trying to remove the obstruction Blood-Brain Barrier consequence of special structure of [cerebral blood vessels] **[Idea: blood-brain barrier is the mechanism that impedes the passage of many toxic substances from the blood into the brain]** - in the rest of the body, the cells that compose the walls of the blood vessels are loosely packed and most tissues pass freely into surrounding tissues - brain: cells are tightly packed, forming a barrier for passage of molecules like proteins and large molecules large molecules critical for brain functions are actively transported through cerebral blood vessel walls blood vessel walls in some areas of the brain allow certain large molecules to pass through the unimpeded - degree to which therapeutic or recreational drugs can influence brain activity depends on the ease with which they penetrate the blood--brain barrier Cells of the Nervous System Anatomy of the Neurons **Neurons:** cells specialized for the reception, conduction and transmission of electrochemical signals **NEURON CELL MEMBRANE** - *lipid bilayer* two layers of fat molecules - inside there are many proteins responsible for the membrane's properties a. *channel proteins* certain molecules pass b. *signal proteins* transfer signal to the inside of the neuron when molecules bind to them on the outside of the membrane **CLASSES OF NEURONS** based on number of processes!! - **Multipolar neuron:** [more than two] process - **Unipolar neuron:** [one] process - **Bipolar neuron:** [two] processes - **Interneuron:** short axon or no axon at all; function is to integrate neural activity within a single brain structure and not to conduct signals from one structure to another  **NEURONS AND NEUROANATOMIC STRUCTURE** two kinds of gross neural structures in the nervous system: 1. **Clusters of bodies: nuclei (CNS) and ganglia (PNS)** - Both a structure in the neuron cell body and a cluster of cell bodies in the CNS 2. **Bundles of axons: tracts (CNS) and** **nerves (PNS)** A diagram of a cell Description automatically generated Glia: The Forgotten Cells **Glial cells**: about 2 for every three neuron in human body Some examples... +-----------------------------------+-----------------------------------+ | 1^st^ class | **Oligodendrocytes** | | | | | | - Glial cells with extensions | | | that wrap around the axons of | | | some neurons of the CNS | | | | | | - Extensions are rich in | | | **myelin**; a fatty | | | insulating substance and the | | | **myelin sheaths** increase | | | the speed of axonal | | | conduction | +===================================+===================================+ | 2^nd^ class | **Schwann cells (in the PNS)** | | | | | | - Each cell constitutes one | | | myelin segment, while | | | oligodendrocytes constitute | | | many, often on more than one | | | axon | | | | | | - Only Schwann cells can guide | | | axonal regeneration | | | (regrowth) after damage | +-----------------------------------+-----------------------------------+ | 3^rd^ class | **Microglia** | | | | | | - Smaller than other cells | | | | | | - respond to injury or disease | | | by multiplying, engulfing | | | cellular debris or even | | | entire cells and they trigger | | | inflammatory responses | +-----------------------------------+-----------------------------------+ | 4^th^ class | **Astrocytes** | | | | | | - Largest glial cells | | | | | | - Star-shaped | | | | | | - Make contact with neurons and | | | some cover the outer surfaces | | | of blood vessels | | | | | | - Play a role in allowing the | | | passage of some chemicals | | | from the blood into CNS | | | neurons and in blocking other | | | chemicals | | | | | | - Have ability to contract or | | | relax blood vessels based on | | | the blood flow demands of | | | particular brain regions | +-----------------------------------+-----------------------------------+ **Some clarifications...** - Physiological effects both numerous and more important than they thought - Much more varied than they are implied by the four types  A close-up of a red blood vessel Description automatically generated Neuroanatomical Techniques and Directions Neuroanatomical techniques **[Issue: neurons are so tightly packed and their axons and dendrites so intricately intertwined that looking through microscope at unprepared neural tissue reveals almost nothing about them ]** **GOLGI STAIN** - Accidental discovery of Golgi stain by Camillo Golgi in the early 1870s - the silver chromate created by the chemical reaction of the two substances Golgi was using invaded a few neurons in each slice of tissue and stained each invaded neuron entirely black. This discovery made it possible to see individual neurons for the first time, although only in silhouette - PROBLEM: provides no indication of the number of neurons in an area **NISSL STAIN** - developed by Franz Nissl, a German psychiatrist, in the 1880s - most common dye is called cresyl violet - they penetrate all cells on a side and they bind to molecules that are most prevalent in neuron cell bodies - they are often used to estimate the number of cell bodies in an area, counting the number of Nissl-stained dots **ELECTRON MICROSCOPY** - neuroanatomical technique that provides information about the details of neuronal structure - limit of magnification is about 1500 times, which is insufficient to reveal the fine anatomical details of neurons - greater detail can be obtained by first coating thin slices of neural tissue with an electron-absorbing substance first coating thin slices of neural tissue with an electron- absorbing substance that is taken up by different parts of neurons to different degrees, then passing a beam of electrons through the tissue onto a photographic film. - A scanning electron microscope has three dimensions but is not capable of as much magnification - PROBLEM OF TRADITIONAL: because they are so detailed, it is difficult to visualise general aspects 1. **Anterograde (forward) tracing methods** - Used when they want to trace the paths of axons projecting **away** from cell bodies located in a particular area **[Steps]** a. Injecting one of several chemicals commonly used **into the cell bodies** b. Then taken up by cell bodies and transported **forward** along their axons to their terminal buttons c. After some days, the investigator removes the brain and slices it d. The slices are then treated to reveal the locations of the injected chemical 2. **Retrograde (backward) tracing methods** - Used when they want to trace the paths of axons projecting **into** a particular area **[Steps]** a. Injecting one of several chemicals commonly used into an **area of the brain** b. These chemicals are taken up by terminal buttons and then transported **backward** along their axons to their cell bodies c. After some days, the investigator removes the brain and slices it d. The slices are then treated to reveal the locations of the injected chemical Directions in the Vertebrate Nervous System **[Idea: they are described in relation to the orientation of the spinal cord ]** **The three axes** 1. **Anterior-posterior** (sometimes known as *rostral* and *caudal*) - Anterior= towards the nose end (anterior end) - Posterior= towards the tail end (posterior end) 2. **Dorsal-ventral** - Dorsal= towards the surface of the back or the top of the head (dorsal surface) - Ventral=towards the surface of the chest or the bottom of the head (ventral surface) 3. **Medial-lateral** - Medial= towards the midline of the body - Lateral= away from the midline towards the body's lateral surfaces - used to refer to the top and bottom of the primate head - proximal= "close" - distal= "far" +-----------------------------------------------------------------------+ | Slices of brain cut in three different planes | | | | 1. **horizontal sections** | | | | 2. **frontal sections (or coronal)** | | | | 3. **sagittal sections** | +-----------------------------------------------------------------------+ - A section cut down the center of the brain, between the two hemispheres, is called a **midsagittal section.** - A section cut at a right angle to any long, narrow structure, such as the spinal cord or a nerve, is called a **cross section** A diagram of the body of a person Description automatically generated Anatomy of the Central Nervous System (CNS) Spinal Cord **Two different areas:** 1. Inner H-shaped core of gray matter 2. A surrounding area of white matter **Gray matter** = composed of largely of cell bodies and [unmyelinated interneurons] a. **Dorsal horns** (the two dorsal arms) b. **Ventral horns** (the two ventral arms) **White matter**= composed of largely of [myelinated axons] CHARACTERISTICS - Pairs of spinal nerves are attached to the spinal cord, one to the left one to the right at 31 different levels of the spine (so 62 spinal nerves that divide near the cord) - The axons of the nerves are joined to the cord via two roots: 1. *The dorsal root* 2. *The ventral root* - [For the dorsal root:] They are all **sensory afferent unipolar neurons** with their cell bodies grouped together just outside the cord to form the **dorsal root ganglia** (some are somatic and some are autonomic) Many of their synaptic terminals are in **the dorsal horns** of the spinal gray matter - [For the ventral root:] They are **motor efferent multipolar neurons** with their cell bodies **in the ventral horns** - Those that are part of the [somatic nervous system] project to [skeletal muscles] - Those that are part of the [autonomic nervous system] project to [ganglia], where they synapse on neurons that in turn project to internal organs Five Major Divisions of the Brain **Early development of brain** - In vertebrate embryo, the tissue that develops into the CNS is recognizable as a fluid-filled tube - First indications of the developing brain are three swellings that occur at the anterior end of this tube. These swellings eventually develop into the adult *forebrain, midbrain and hindbrain* - Before birth, the initial three swellings in the neural tube become five because the forebrain and the hindbrain divide into two - Five swellings that compose the developing brain at birth are (these ultimately develop into the five divisions of the adult brain): 1. *Telencephalon* undergoes the biggest growth during development 2. *Diencephalon* 3. *Mesencephalon (midbrain)* 4. *Metencephalon* 5. *Myelencephalon* often referred as *medulla* encephalon means "within the head" 2,3,4,5 are often referred collectively as **brain stem**, where the cerebral hemispheres sit. A diagram of the human brain Description automatically generated  Myelencephalon (medulla) - The most posterior division of the brain - Composed largely of tracts carrying signals between the rest of the brain and the body - **Reticular formation**: complex network of about 100 nuclei that occupies the central core of the brain stem from the posterior boundary of the myelencephalon to the anterior boundary of the midbrain called like this due to its netlike appearance sometimes called the reticular activating system because it seems to play a role in arousal but the various nuclei play a role in a variety of functions like sleep, attention, movement, the maintenance of muscle tone etc. Metencephalon - Houses many ascending/descending tracts and part of the reticular formation - These structures create a bulge called the **pons**, on the brain stem's ventral surface - The other major division is called **cerebellum** (little brain), which is a large, convoluted structure on the brain stem's dorsal surface important sensorimotor structure cerebellar damage eliminated ability to precisely control one's movements and adapt them to changing conditions but it is not restricted to sensorimotor control, as there is cognitive deficit Mesencephalon - two divisions 1. **Tectum** The dorsal surface of the midbrain has two pairs of bumps: a. [Posterior pair]: **inferior colliculi**= has an auditory function b. [Anterior pair]: **Superior colliculi**= has a visual-motor function, more specifically to direct the body's orientation toward or away from particular visual stimuli in lower vertebrates, the function of the tectum is entirely visual-motor, and it's sometimes referred to as *optic tectum* 2. **Tegmentum** - The division of the mesencephalon ventral to the tectum - Adding to the reticular formation and tracts of passage, the tegmentum contains three colourful structures of particular interest to biopsychologists: a. **the periaqueductal gray**= gray matter situated around the cerebral aqueduct, the duct connecting the third and fourth ventricles of special interest because it has the role in mediating the analgesic (pain-reducing) effects of opioid drugs b. **the substantia nigra** c. **and the red nucleus** both important components of the sensorimotor system  Diencephalon Two structures 1. **thalamus** - large, two-lobed structure that constitutes the top of the brain stem - one love on each side of the third ventricle and the two lobes are joined by the **Massa intermedia**, which runs through the ventricle - there is visible *lamina (layers)* on the surface of the thalamus that are composed of myelinated axons - there are many different pairs of nuclei most of which project to the cortex - **sensory relay nuclei**: receives signals from sensory receptors, process them and then transmit them in the appropriate areas of sensory cortex they all receive feedback signals from the very areas of cortex which they project the majority of them receive input from areas of the cortex and project to other areas of the cortex [i.e. **the lateral geniculate nuclei, the medial geniculate nuclei and the ventral posterior nuclei** are important relay stations in the visual, auditory and somatosensory systems respectively ] 2. **hypothalamus** [location]: just below the ante-thalamus [role]: regulation of several motivated behaviours [i.e. sleeps and eat] - Exerts its effects in part by regulating the release hormones from **pituitary glands** ("snot gland"), which dangles from it on the ventral surface of the brain - [Two other structures on the inferior surface of the hypothalamus:] a. **Optic chiasm**= point at which the *optic nerves* from each eye come together and then decussate (cross over to the other side of the brain) **decussating fibers** are said to be **contralateral** (projecting from one side of the body to the other) **nonndecussating fibers** are said to be **ipsilateral** (staying on the same side of the body) b. **Mammillary bodies**= considered a part of hypothalamus; are a pair of spherical nuclei located on the inferior surface of the hypothalamus, just behind the pituitary  Telencephalon the largest division of the human brain [Role]: mediates the brain's most complex functions initiates voluntary movement, interprets sensory input and mediates complex cognitive processes such as learning, speaking and problem solving **CEREBRAL CORTEX OR BARK** (layer tissue) - Because the cerebral cortex is mainly composed of small, unmyelinated neurons, it is gray and is often referred to as the *gray matter.* - In contrast, the layer beneath the cortex is mainly composed of large, myelinated axons, which are white and often referred to as the *white matter*. - [In humans:] it is deeply convoluted/ furrowed, and these *convolutions* have the effect of increasing the amount of cerebral cortex without increasing the overall volume of the brain not all mammals have convoluted though; some are *lissencephalic* (smooth-brained) it is mainly the body size; [the largest, the more the convolutions] [large furrows]: **fissures**, [small furrows]: **sulci**, [the ones in between]: **gyri** the largest fissure is called **longitudinal fissure** and separates the cerebral hemisphere - The cerebral hemispheres are directly connected by a few tracts spanning the longitudinal fissure and these are called **cerebral commissures**. The largest of them is called **corpus callosum**. - [The two major landmarks of the lateral surface of each hemisphere:]\ 1. **Central fissure** 2\. **lateral fissure** these divide each hemisphere into four lobes: a. **Frontal lobe** b. **Parietal lobe** c. **Temporal lobe** d. **Occipital lobe** **Note: they are not functional units** Among the largest gyri... a. **Precentral gyri** b. **Postcentral gyri** c. **Superior temporal gyri** +-----------------------------------+-----------------------------------+ | Lobes | Function | +===================================+===================================+ | **Occipital lobe** (the occipital | Analysis if visual input to guide | | cortex and large areas of | our behaviour | | adjacent cortex) | | +-----------------------------------+-----------------------------------+ | **parietal lobe** (two functional | [1) Postcentral | | areas) | gyrus:] analyses | | | sensations from the body | | | | | | [2) Remaining areas of cortex in | | | posterior parts of parietal | | | lobes]: play a role | | | in perceiving the location of | | | both objects and our own bodies | | | and in directing our attention | +-----------------------------------+-----------------------------------+ | **temporal lobe** (three | 1. [superior temporal | | functional areas) | gyrus:] involved | | | in hearing and language, the | | | | | | 2. [inferior temporal | | | cortex:] | | | identifies complex visual | | | patterns | | | | | | 3. [the medial portion of | | | temporal cortex:] | | | important for certain kinds | | | of memory | +-----------------------------------+-----------------------------------+ | **Frontal lobe** (two functional | 1. [Precentral gyrus and | | areas) | adjacent frontal | | | cortex:] a motor | | | function | | | | | | 2. [the frontal cortex | | | ] | | | | | | [anterior to motor | | | cortex:] performs | | | complex cognitive functions, | | | | | | [i.e. such as planning response | | | sequences, evaluating the | | | outcomes of potential patterns of | | | behavior, and assessing the | | | significance of the behavior of | | | others] | +-----------------------------------+-----------------------------------+ NEOCORTEX - About 90% is of the human cerebral cortex is **neocortex** (or *isocortex)* - *The layers of neocortex are numbered I through VI* Characteristics 1. Many cortical neurons fall into one of two different categories: a. **pyramidal cells** (pyramid-shaped) \- large multipolar neurons with a large dendrite called *apical dendrite* that extends from the apex of the pyramid straight toward the cortex surface and a very long axon b\. **stellate cells** (star-shaped) \- small interneurons (short or no axon) 2. The six layers of neocortex differ from one another in terms of the size and density of their cell bodies and the relative proportion of pyramidal and stellate cell bodies that they contain. 3. Many long axons and dendrites course vertically through the neocortex [i.e. at right angles to the cortical layers] this vertical flow of information is the basis of the neocortex's **columnar organization**: Neurons in a given vertical column of neocortex often form a mini circuit that performs a single function 4. Although neocortex is six-layered, there are variations in the thickness of the respective layers from area to area [i.e. the stellate cells of layer IV are specialized for receiving sensory signals from the thalamus, layer IV is extremely thick in areas of sensory cortex. Conversely, because the pyramidal cells of layer V conduct signals from the neocortex to the brain stem and spinal cord, layer V is extremely thick in areas of motor cortex.] OTHER AREAS \- **hippocampus** is an important area of the cortex that is not neocortex and has three major layers located at the [medial edge of the cerebral cortex] as it folds back on itself in the medial temporal lobe [role:] in some kinds of memory Limbic System and the Basal Ganglia **[Idea: there are several large subcortical nuclear groups some considered part of the *limbic system* and some of the *basal ganglia system* ]** - **Limbic system**= circuit of midline structures that circle the thalamus is involved in regulation of motivated behaviours [(the four Fs fleeing, feeding, fighting and sexual behaviour)] major structures include [the amygdala, the fornix, the cingulate cortex and the septum + the mammillary bodies and the hippocampus] +-----------------------------------+-----------------------------------+ | Structure | Place/ function | +===================================+===================================+ | **Amygdala** | Almond-shaped nucleus in the | | | anterior temporal lobe. | | | | | | Posterior to the amygdala is the | | | hippocampus, while runs beneath | | | the thalamus in the medial | | | temporal lobe | | | | | | Function: Emotion, [particularly | | | fear] | +-----------------------------------+-----------------------------------+ | **Cingulate cortex** | Large strip of cortex in the | | | **cingulate gyrus** on the medial | | | surface of the cerebral | | | hemispheres, just superior to the | | | corpus callosum; it encircles the | | | dorsal thalamus | +-----------------------------------+-----------------------------------+ | **Fornix** | It is the major tract of the | | | limbic system and also encircles | | | the dorsal thalamus. | | | | | | it leaves the dorsal end of the | | | hippocampus and sweeps forward in | | | an arc coursing along the | | | superior surface of | | | | | | the third ventricle and | | | terminating in the septum and the | | | mammillary bodies. | +-----------------------------------+-----------------------------------+ | **Septum** | Is a midline nucleus located in | | | the anterior tip of the cingulate | | | cortex. | | | | | | Several tracts connect the septum | | | and mammillary bodies with the | | | amygdala and hippocampus, thereby | | | connecting the limbic ring. | +-----------------------------------+-----------------------------------+ **Hippocampus**= certain forms of memory **Hypothalamus**= variety of motivated behaviours such as eating and sleeping **Basal ganglia**= role in the performance of voluntary motor responses and decision making Areas of interest 1. the striatum from the substantia nigra of the midbrain: *Parkinson's disease*, a disorder characterized by rigidity, tremors, and poverty of voluntary movement, is associated with the deterioration of this pathway. 2. *Nucleus accumbens*= medial portion of the ventral striatum and plays a role in the rewarding effects of addictive drugs and other reinforcers - The long tail-like **caudate** and **putamen** receive inputs from the neocortex those two are known as **striatum** (striped structure). Its main output is to a pale circular structure known as the globus **pallidus** (pale globe) which is located medial to the putamen between the putamen and the thalamus   **Kalat, module 1.2, pages 14-22** Neurons and Other Cells Neurons **[Idea: the nervous system consists of two kinds of cells: neurons and glia ]** **Neurons**: receive information and transmit it to other cells - The adult human brain has approximately 86 billion neurons but it really varies **Santiago Ramon y Cajal, a Pioneer of Neuroscience** 1852-1934 - Combines artistry with medicine by doing drawings of the nervous system - Introduced the idea that the brain consists of individual cells - Used Golgi's method and applied it to infant brains, which are easier to examine when slicing [opposite conclusion:] Nerve cells remain separate instead of merging into one another. A small gap separates. The tip of a neuron's fiber from the surface of the next neuron. The brain, like the rest of the body, does indeed consist of individual cells. **More** - During the 1800s they discovered that the body consists of cells and they found out that cells are either roundish or elongated - When examining the brain, they found cells that looked nothing like the others, with long fibers stretching from one place to another - Late 1800s**, Camillo Golgi**: found a way to stain nerve cells with silver salts, so they started examining the structure of a single cell. [conclusion:] the fibers of the brain all link together and that the brain is like a mesh without separate cells. - Both won Nobel prizes and never agreed with each other! The Structures of an Animal Cell - In a neuron, the surface of a cell is its membrane (plasma membrane) and separates the cell from the outside environment protein channels in the membrane permit a controlled flow of water, oxygen, sodium, potassium, calcium, chloride and other important chemicals - Expect from RBCs, all animal cells have a nucleus that contain chromosomes. The DNA is not stable for long in water solution so this and other chemicals are carefully scaffolded by other chemicals - Cells contain **ribosomes**, structures than synthesize new protein molecules a. Some float freely b. Other attach to the **endoplasmic reticulum**, a network of thin tubes that transport newly synthesized - A **mitochondrion** performs metabolic activities and provides energy for cell activities have their own genes, separate from those in the nucleus of a cell inherited in the cytoplasm of an egg cell (so from the mother) brain dependent on them [ their activity can be altered from genes or from toxic chemicals, stress or illnesses that produce inflammation] [ decreased mitochondrial function means decreased mental energy and high probability of depression and there is also link with epilepsy, Alzheimer, Parkinson and Huntington disease.] The Structure of Neurons highly variable shape - [All include a soma and most have:] 1. **Dendrites** 2. **Axon** 3. **a presynaptic terminal** - The tiniest neurons lack of axons and some neurons lack well-defined dendrites a. **Motor neuron (efferent to nervous system)**: with its soma in the spinal cord, receives excitation through its dendrites and conducts impulses along its axon to a muscle. b. **Sensory neuron (afferent to nervous system)**: is specialized at one end to be highly sensitive to a particular type of stimulation, such as touch - **Cell body or soma** contains the nucleus, ribosomes and mitochondria range in diameter from 0.005 millimeter (mm) to 0.1 mm in mammals and up to 1 mm in some vertebrates in many neurons, it is covered with synapses +-----------------------------------------------------------------------+ | 4. **Dendrites** | | | | Are branching fibers that get narrowed near their ends (**Giorgio | | Ascoli 2015**) | | | | dendrite's surface is lined with specialized *synaptic receptors*, at | | which the dendrite receives information from other neurons. | | | | many contain **dendritic spines**, short outgrows that increase the | | SA available for synapses | +=======================================================================+ | 1. Axon | | | | A thin fiber of constant diameter and conveys an impulse to other | | neurons, an organ or a muscle | | | | some extent more than a meter like the one from your spinal cord to | | your feet | | | | many vertebrate axons are covered with the insulating material called | | myelin sheath and the interruptions are called nodes of Ranvier. | | Intervertebrate axons do not have them | | | | a neuron can have **one** axon which many have branches | | | | the end of each branch has a swe | | | | 2. Presynaptic terminal (end bulb or bouton) | | | | It is the swelling in the end of each branch in an axon | | | | there, the axon releases chemicals that cross to another cell | +-----------------------------------------------------------------------+ | 3. OTHER STRUCTURES | | | | - **Afferent axon**: brings information **into** the structure | | | | - **Efferent axon**: carries information **away** from a structure | | | | - If a cell's dendrites and axon are entirely contained within a | | single structure, the cell is an interneuron or intrinsic neuron | | of the structure. | +-----------------------------------------------------------------------+ - In size, shape and function - Shape determines its connections with other cells and thereby determines its function the branching dendrites of the Purkinje cell cerebellum enable it to receive input from up to 200,000 other neurons. -  By contrast, the tiny bipolar neurons in the retina might receive input from as few as two other cells. Glia 1. **Astrocytes** generation of rhythms and also dilate the blood vessels to bring more nutrients into the most active brain areas - A single astrocyte might surround the tips of a few hundred dendrites. - By surrounding a connection between neurons, an astrocyte shields it from chemicals circulating in the surround - by taking up the ions and transmitters released by axons and then releasing them back, an astrocyte helps synchronize closely related neurons, enabling their axons to send messages in waves - in some brain areas, they also respond to hormones - *tripartite synapse*: tip of axon releases chemicals that cause the neighbouring astrocyte to release its own chemicals, thus modifying the message to the next neuron - also control the critical period for modification of the visual cortex early in life 2. **Microglia** remove viruses and fungi from the brain - After brain damage, the remove dead/damaged neurons - With astrocytes, they prune ineffective synapses and adjust effectiveness of others and wrong pruning can lead to developmental disorders - They also provide negative feedback to put the brakes on neuronal activity - Loss if microglia leads to seizures 3. **Oligodendrocytes** in brain and spinal cord respond to neural activity by altering the myelin sheaths and thus the timing of axons' responses they participate in certain types of learning and memory 4. **Schwann cells** in the periphery of the body build the myelin sheaths that surround and insulate certain vertebrate axons. - Supply axon with nutrients necessary for proper functioning 5. **Radial glia** guide the migration of neurons and their axons and dendrites during embryonic development A diagram of neurons and neurons Description automatically generatedThe Blood-Brain Barrier (in the vertebrate brain) exclude certain chemicals from the blood to pass to the brain Why we need it? - When a virus invades a cell, certain mechanisms help the immune system to find them, kill them and the cell that contains them, so a cell exposes a virus through its membrane - This works well if the virus-infected cell is a skin cell or a blood cell than can be replaced easily BUT the vertebrate brain cannot replacer damaged neurons - To minimise the risk, **the body lines the brain's blood vessels with tightly packed cells** **that keep out most viruses and bacteria.** - Few viruses do manage to pass however, **so the microglia attack most viruses that enter the nervous system, mounting an inflammatory response that fights the virus without killing the neuron control but no elimination!!** [i.e. spirochete responsible for syphilis can penetrate the blood-brain barrier, producing long-lasting and potentially fatal consequences if not properly treat ] - Even if the virus does not cross the blood--brain barrier, it could harm the brain by constricting capillaries, thus decreasing blood flow to the brain, and by triggering a great increase in the immune response How does it works? - Depends on endothelial cells that form the walls of the capillaries - Outside the brain, cells along the capillaries are separated by small gaps, but in the brain, they join so tightly that they block almost anything from passage. - How fast a drug crosses the blood--brain barrier determines how fast it affects behaviour i.e. chemotherapy drugs can't cross the barrier, making hard to treat brain cancer - H2O crosses through special protein channels in walls of endothelial cells - Sodium, potassium and chloride ions also cross through specific channels - The brain uses active transport, a protein-mediated process that expends energy, to pump glucose, amino acids (the building blocks of proteins), omega-3 fatty acids, and several vitamins from the blood into the brain. The membrane also has mechanisms to transport ketones and several hormones into the brain - Tends to become less efficient with age, especially when Alzheimer **Nourishment of Vertebrate Neurons** - Vertebrate brain cells depend almost entirely on **glucose** and also cancer and testis cells. - Brain cells can also rely on [ketones and lactate,] but they don't reach the brain in sufficient quantity - For glucose, neurons need a [steady supply of oxygen ] [brain uses about 20 % of body's oxygen and 25% of glucose ] - [Glucose shortage] only during starvation liver makes a glucose from many carbohydrates, amino acids, glycerol - [Inability to use glucose] can be a problem body needs vitamin B, **thiamine** lack of it leads to death of neurons and condition called *Korsakoff's syndrome*, marked from memory impairments - The bacteria in the gut are 'guests', on probably one-to-one ratio - They influence the [brain activity] 1. stimulate the [vagus nerve], which runs from the intestines to the brain 2. release chemicals that cross the lining of the intestines and enter the blood vitamins, amino acids and ones that cause inflammation affect mood and motivations - stress increases the type of bacteria that cause inflammation and mitochondrial damage - people with [depression] have more of those bacteria and less with anti-inflammatory effects [antidepressants] attack bacteria but it is not a good idea to remove all intestinal ones because it increases anxiety and depression so it is good to also take [probiotics ]  **Kalat, module 3.1, pages 66-78** Structure of the Vertebrate Nervous System - **Central Nervous System (CNS)** - **Peripheral Nervous System (PNS)** 1. **Somatic** 2. **Autonomic** a. **Enteric** Directions **Dorsal-ventral** - the dorsal--ventral axis of the human brain is at a right angle to the dorsal--ventral axis of the spinal cord. 1. **Horizontal** 2. **Sagittal** 3. **Coronal/ frontal**  **The Spinal Cord** The spinal cord communicates with all the sense organs and muscles except those of the head. It is a segmented structure, and each segment has on left and right sides a sensory nerve and a motor nerve, - **entering dorsal roots (axon bundles):** carry [sensory] information - **the exiting ventral roots**: carry [motor] information. The cell bodies of the sensory neurons are in [clusters of neurons outside the spinal cord], called the dorsal root ganglia Cell bodies of the motor neurons are [inside the spinal cord.] The H-shaped **gray matter** in the center of the cord is densely packed with cell bodies and dendrites. neurons from the gray matter of spinal cord send axons to the brain or to other parts of spinal cord through the **white matter** which contains myelinated axons **Clarifications** - Each segment of the spinal cord sends sensory information to the brain and receives motor commands from the brain. - All that information passes through tracts of axons in the spinal cord. If the spinal cord is cut at a given segment, the brain loses sensation from that segment and below. -  The brain also loses motor control over all parts of the body served by that segment and the lower ones. **The Autonomic Nervous System** **Sympathetic Nervous System (SNS)** - a network of nerves that prepare the organs for a burst of vigorous activity, consists of chains of ganglia just to the left and right of the spinal cord's central regions. - These ganglia have connections back and forth with the spinal cord. - Sympathetic axons prepare the organs for "fight or flight," such as by increasing breathing and heart rate and decreasing digestive activity - Because the sympathetic ganglia are closely linked, they often act as a single - system "in sympathy" with one another, although certain events activate some parts more than others. - The sweat glands, adrenal glands, muscles that constrict blood vessels, and muscles that erect the hairs of the skin have sympathetic input but no parasympathetic input - Most axons release **norepinephrine but some, like sweat glands, also release acetycholine** **Parasympathetic Nervous System (PNS)** - facilitates vegetative, nonemergency responses. - parasympathetic activities are related to, and generally the opposite of, sympathetic activities. - The parasympathetic system also promotes sexual arousal, including erection in males. - also known as the **craniosacral system** because it consists of the [cranial nerves and nerves from the sacral spinal cord] - the parasympathetic ganglia are not arranged in a chain near the spinal cord. Rather, long *preganglionic* axons extend from the spinal cord to parasympathetic ganglia close to each organ. Shorter postganglionic fibers then extend from the parasympathetic ganglia into the organs themselves. here, the ganglia act more independently than in sympathetic - Parasympathetic activity [decreases heart rate, increases digestive rate, and, in general, conserves energy] - The parasympathetic nervous system's axons release the **neurotransmitter acetylcholine** onto the organs.  +-----------------------------------------------------------------------+ | **BOTH** | | | | - Are constantly active and many stimuli arouse both | | | | - Drugs act differently for the two systems | +-----------------------------------------------------------------------+ **Brain divisions** 1. Hindbrain (rhombencephalon) 2. Midbrain (mesencephalon) 3. Forebrain (prosencephalon **The Hindbrain** - the posterior part of the brain, consists of **the medulla, the pons, and the cerebellum.** - The medulla and pons, the midbrain, and certain central structures of the forebrain constitute the **brainstem** - **The medulla** can be regarded as an enlarged extension of the spinal cord. The head and the organs connect to the medulla and adjacent areas by **12 pairs of cranial nerves** their size varies among species they control vital reflexes like breathing and vomiting opiate receptors can produce a dangerous decrease in the breathing and heart rate [i.e. In elephants, the trigeminal nerve that receives sensations from the face is huge because it innervates the trunk, a highly sensitive structure for elephants. The elephant's trigeminal nerve is thicker than its spinal cord!] \- **The pons** lies anterior and ventral to the medulla. Like he medulla, it contains nuclei for several cranial nerves. in the pons, axons from each half of the brain cross to the opposite side of the spinal cord so that the left hemisphere controls the muscles of the right side of the body and the right hemisphere controls the left side.  - **The cerebellum** a large hindbrain structure with many deep folds. It is one of the first brain areas to start developing and one of the last to complete development. [contributes to control of movement, balance and coordination] People with damage to the cerebellum have difficulty with timing, such as judging whether one rhythm is faster than another rhythm. Depending on the location and type of damage, they may have impairments of learning, memory, attention, visual-spatial processing, language, recognizing emotional expressions, or social behaviour. - Also predicting sequence of events  **The Midbrain** - is between the hindbrain and the forebrain, although in adult mammals the forebrain surrounds it. - The midbrain is more prominent in reptiles, amphibians, and fish. - The roof of the midbrain is called the **tectum.** The swellings on each side of the tectum are the **superior colliculus** and the **inferior colliculus** Both are important for [sensory processing]---[the inferior colliculus for hearing and the superior colliculus for vision.] - Under the tectum lies the **tegmentum**, the intermediate level of the midbrain - the **substantia nigra**, gives rise to a dopamine-containing pathway that facilitates readiness for movement. **The Forebrain** - the most prominent brain area for mammals and birds, consists of two cerebral hemispheres, left and right. - Each hemisphere is organized to receive [sensory information], mostly from the contralateral (opposite) side of the body. - It controls muscles, mostly on the contralateral side, by way of axons to the spinal cord and the cranial nerve nuclei. - The outer portion is the [cerebral cortex.] below, there are other structures the **thalamus** is the [main source of input to the cortex] The **hypothalamus** is [essential for control of eating, drinking, temperature control, and reproductive behaviours. ] The **amygdala** is part of a circuit that is [central for evaluating emotional information, especially with regard to fear.]  Thalamus - Pair of structures in center of forebrain - Most sensory information goes first to the thalamus, which processes it and sends output to the cerebral cortex. - An exception to this rule is olfactory information, which goes from the olfactory receptors to the olfactory bulbs and then directly to the cerebral cortex. - Many nuclei of the thalamus receive their input from a sensory system, such as vision, process it in various ways, and transmit information to an area of the cerebral cortex - When you hold information in working memory, activity bounces back and forth between the frontal cortex and the thalamus (so role in memory) Hypothalamus and Pituitary Gland - Hypothalamus is a small area just ventral to the thalamus and has widespread connections with the rest of the brain - [Damage] in the hypothalamus leads to abnormalities in motivated behaviours, such as feeding, drinking, temperature regulation, sexual behaviour, or fighting. - Partly through nerves and partly by releasing hormones, the hypothalamus conveys messages to the **pituitary gland**, altering its release of hormones Basal Ganglia - a group of subcortical structures lateral to the thalamus, include the **caudate nucleus, the putamen, and the globus pallidus** (authorities also include other structures like the nucleus accumbens) - It has long been known that [damage to the basal ganglia impairs movement, as in conditions such as Parkinson's disease and Huntington's disease] - [The basal ganglia integrate motivational and emotional behaviour to increase the ] [vigour of selected actions. ] - However, the role of the basal ganglia extends beyond movement. [They are critical for ] - [gradual learning of skills and habits.] Basal Forebrain - A structure on the ventral surface of the forebrain, the nucleus basalis, receives input from the hypothalamus and basal ganglia and sends axons that release acetylcholine to widespread areas in the cerebral cortex. - The nucleus basalis is a key system for arousal, wakefulness, and attention. Patients with Parkinson's disease and - Alzheimer's disease has impairments of attention and intellect because of inactivity or deterioration in the nucleus basalis. Hippocampus - is a large structure between the thalamus and the cerebral cortex, mostly toward the posterior of the forebrain - [the hippocampus is critical for memories, especially memories for individual events. ] [It is also essential for monitoring where you are and where you are going.]  **The Ventricles** Four fluid-filles cavities within the brain, each ventricle has two - Toward their posterior, they connect to the third ventricle, positioned at the midline, separating the left and right thalamus. - - The third ventricle connects to the fourth ventricle in the center of the medulla. - Cells called the choroid plexus along the walls of the four ventricles produce **cerebrospinal fluid (CSF),** a clear fluid similar to blood plasma. CSF flows from the lateral ventricles to the third and fourth ventricles, and then into the central canal of the spinal cord and the narrow spaces between the brain and the **meninges**, membranes that surround the brain and spinal cord. Although the brain has no pain receptors, the meninges do, and meningitis---inflammation of the meninges---is painful. Swollen blood vessels in the meninges produce the pain of a migraine headache. Cerebrospinal fluid cushions the brain against mechanical shock when the head moves. It also provides buoyancy. Just as a person weighs less in water than on land cerebrospinal fluid helps support the weight of the brain. It also provides a reservoir of hormones and nutrition for the brain and spinal cord. If the flow of CSF is obstructed, it accumulates in the ventricles or in the space between brain and meninges, increasing pressure on the brain. When this occurs in infants, the skull bones spread, causing an overgrown head. This condition, known as **hydrocephalus,** can impair cognitive development, although the results vary from one person to another. A close-up of a diagram Description automatically generated  **Kalat, module 3.2, pages 81-88** **The Cerebral Cortex** the largest part of the mammalian brain; occupies about 10-14% of the brain in nearly all species - The cells on the outer surface of the cerebral cortex are gray matter, and their axons extending inward are white matter - Neurons in each hemisphere communicate with the corresponding part of the other hemisphere through two bundles of axons, the **corpus callosum** and the **smaller anterior commissure** Several other commissures (pathways across the midline) link subcortical structures. - Basic organization is the same in most mammalians, but they vary in size a. Size of cerebral cortex b. Degree of folding primates have a larger cerebral cortex, more folding, and more neurons per unit of volume [i.e. Larger animals, such as elephants, have larger brain size but also larger neurons and fewer neurons per unit of volume. Humans have almost three times as many neurons in the cerebral cortex as elephants have, although the elephant brain is more than twice as large.] - [as the proportion devoted to the forebrain increases, the relative sizes of the midbrain and medulla decrease.] That is, humans and other primates have a larger than average cerebral cortex, in proportion to the rest of the brain. - Most species have about 4 neurons in the cerebellum for everyone in the cerebral cortex A close-up of several human brain Description automatically generated A diagram of the human brain Description automatically generated Organization of the Cerebral Cortex - In humans and most other mammals, the cerebral cortex contains up to six distinct **laminae**, layers of cell bodies parallel to the surface of the cortex - The laminae vary in prominence from one part of the cortex to another, and a given lamina may be absent from certain areas. [Lamina IV] receives sensory info is prominent in sensory areas of cortex but absent in motor [Lamina V] sends long axons to the spinal cord and is thickest in the motor cortex [layer I] has many axons and dendrites, but few cells is a site for many connections, especially for those in learning The cells within a column have similar properties to one another [i.e. If one cell responds to a horizontal pattern of light at a particular location, then other cells in the column respond to the same pattern in nearby locations] The Occipital Lobe - Located at the **posterior** end of the cortex, it is the main target for **visual information**. - **Primary visual cortex (striate cortex)**: Found in the **posterior occipital lobe**, known for its **striped appearance** in cross-sections. - **Right hemisphere damage**: Causes **blindness in the left visual field** (from the viewer's perspective). - **Cortical blindness**: Results from damage to the visual cortex, leading to **no conscious visual perception** or **visual imagery**, even in dreams. **Eye damage vs. cortical damage**: - Eye damage: Leads to blindness, but intact occipital cortex allows for **visual imagery** and **visual dreams** (if previous visual experience exists). - Cortical damage: Eliminates both **visual perception** and **visual imagery**. - **Summary**: **Eyes provide stimuli**, but the **visual cortex** creates the experience. The Parietal Lobe - Located between the **occipital lobe** and the **central sulcus** (a deep cortical groove). - **Postcentral gyrus (primary somatosensory cortex)**: Found just posterior to the central sulcus, it receives input from **touch receptors**, **muscle stretch receptors**, and **joint receptors**. - **Stimulating the postcentral gyrus**: During surgery with local anesthesia, stimulation can cause **tingling sensations** on the **opposite side of the body**. - **Cellular organization**: The postcentral gyrus consists of **four parallel bands of cells**, each processing sensory information differently: - **Body representation**: The postcentral gyrus **maps the body four times** to process sensory information. - **Role in sensory integration**: Information about **touch and body location** aids in interpreting **visual** and **auditory inputs** by contextualizing spatial relationships. - **Monitoring positions**: The parietal lobe tracks **eye**, **head**, and **body positions**, sharing this data with movement-controlling brain areas. - **Spatial and numerical processing**: Critical for understanding **spatial information** and **numerical concepts**, reflecting their overlap (e.g., counting on fingers). The Temporal Lobe - Located in the **lateral portion** of each hemisphere, near the **temples**, and the main cortical target for **auditory information**. - **Speech processing**: The **left temporal lobe** is essential for **speech** in most people. - **Visual contributions**: Involved in **movement perception** and **recognition of faces** and objects. - **Hallucinations and schizophrenia**: **Thinner auditory cortex** in the left temporal lobe is linked to frequent hallucinations. - **Emotion and motivation**: Plays a key role in **emotional and motivational behaviors**. - **Klüver-Bucy syndrome**: Temporal lobe damage can cause behaviors such as: - **Temporoparietal junction**: Found at the intersection of the **parietal**, **temporal**, and **occipital lobes**, it integrates **vision, hearing, and body senses**. - **Social cognition and body awareness**: Damage, particularly in the **right hemisphere**, impairs imagining another person's perspective and affects **attention** and **body awareness**. The Frontal Lobe - Extends from the **central sulcus** to the **anterior brain**, containing the **primary motor cortex** and **prefrontal cortex**. - **Precentral gyrus (primary motor cortex)**: - **Prefrontal cortex**: The **most anterior part** of the frontal lobe. - **Default network**: - **Significance of daydreaming**: Prepares the brain for future decisions and consolidates experiences into memories.  A diagram of the human brain Description automatically generated  - surgery that consisted of damaging the prefrontal cortex or cutting its connections to the rest of the cortex - believed it would help with severe psychiatric disorders - in 1949 the most prominent practitioner, **Egaz Moniz,** received a Nobel Prize for his work on lobotomy, one of the most embarrassing and regrettable decisions in the history of the prize. - **Walter Freeman**, a medical doctor untrained in surgery started of with schizophrenia but then moved to healthier people - Symptoms: apathy, lack of initiative, memory disorders, distractibility, and a loss of emotional expressions. Also, impulsiveness Functions of Prefrontal Cortex - Analysis of **three major regions** of the **prefrontal cortex**: posterior, middle, and anterior. 1. **Posterior portion** primarily linked to **movement**. 2. **Middle zone** associated with **cognitive control**, **emotional responses**, and certain **memory functions** - Damage to the **middle zone** impairs the ability to infer relationships (e.g., A \> B, B \> C, but not A \> C). - Individuals with **middle zone damage** form **memories** but struggle to **apply them in new situations**. 3. **Anterior zone** critical for **decision-making** and evaluating actions for **optimal outcomes**. - **Decision-making** involves assessing **action difficulty**, **success/failure probabilities**, and **reward value** (e.g., reward relevance depending on circumstances). - **Prefrontal cortex cells** factor in **complex variables**, such as **current needs** and **future rewards**. - Damage to the **anterior zone** often results in **impulsive decision-making** due to difficulty **weighing pros and cons**. Beyond Gray Matter: The Connections **The Humane Connectome Project** - an effort to map all the long-distance connections, analogous to the way the human genome project mapped all the genes on the chromosomes. - Researchers have already demonstrated many correlations between brain connections and behavioural tendencies, and they expect to find abnormal connections responsible for many psychological disorders How Do The Parts Work Together? - Vision, touch, and hearing activate cortical areas that have only weak connections with one another. - **Binding problem/ large-scale integration problem:** question of how various brain areas produce a perception of a single object - Few cells combine one sense with another - Although no one can fully explain binding, we know what is necessary for it to occur: It occurs if you perceive two sensations as happening at the same time at approximately the same place. **Two experiments...** A diagram of two people Description automatically generated  A screenshot of a book Description automatically generated