Anatomy Note (CPM 282) PDF

# Neurochemistry for Pharmacy Students (cpm 282) ## Topic: Neurons ### Lecturer: Mr. Ezeugwy ### Date: Tue, 5th Nov 2024. ### Duration: 8:00-10:00 - The neuron is the basic working unit of the brain. It is a specialized cell designed to transmit information to other nerve cells, muscle, and gland...

# Neurochemistry for Pharmacy Students (cpm 282) ## Topic: Neurons ### Lecturer: Mr. Ezeugwy ### Date: Tue, 5th Nov 2024. ### Duration: 8:00-10:00 - The neuron is the basic working unit of the brain. It is a specialized cell designed to transmit information to other nerve cells, muscle, and gland cells. - Neurons are cells within the nervous system that transmit information to other cells, muscle, and gland cells. - Most neurons have a cell body, an axon, and dendrites. - Neurons send and receive signals from your brain. - While neurons have a lot in common with other types of cells, they are structurally and functionally unique. - Specialized projections called axons allow neurons to transmit electrical and chemical signals to other cells. - Neurons can also receive this signals via routes like projections known as dendrites. - At birth, the human brain consists of an estimated hundred billion neurons. Unlike other cells, neurons do not regenerate. - They are not replaced once they die, but generation of new nerve cells is called Neurogenesis, which the process is not well understood. - It occurs in some parts of the brain after birth. ### Parts of a Neuron - Neurons vary in size, shape, and structure depending on their role and location. However, nearly all neurons have 3 parts: - A Cell Body - An Axon - Dendrite ### Cell Body - This is also known as a *SOMA*. - The cell body is the neuron's core. - The cell body carries genetic information, maintains neuron structure, and provides energy to drive activities. - Like other cell bodies, the neuron are specialized organelles. - It is enclosed by the membrane, which bolsters protection and allows it to interact with its immediate surroundings. ### Axon - An axon is a long, tail-like structure, which joins the cell body at a specialized junction called the *AXON HILLOCK*. - Many axons are insulated with a fatty acid substance called *Myelin*. ### Dendrites - These are fibrous roots that branch out from their cell body. - They receive and process signals from axons of other neurons. - Neurons can have more than one set of dendrites known as *Dendritic Tree*. - However, the much they have generally depend on their roles. - For instance, the Purkinje cell are special type of neuron found in the cerebellum. - This cell have highly developed dendritic tree which allows them to receive thousands of signals. ### Functions of Neurons - Neurons send signals using action potentials. - An action potential is a shift in neurons’ electrical potential caused by the flow of ions in and out of the neuronal membrane. - Action potential can trigger both chemical and electrical synapses. ### Types of Neurons - Neurons vary in structure, function, and genetic makeup giving the sheer number of neurons. - There are thousands of different types of neurons, much like there are thousands of species of living organisms on earth. - In terms of function, there are three (3) types: - **Sensory Neurons** - This helps in taste, smell heat, see, feel things. - Sensory neurons are triggered by physical and chemical inputs from the environment; sound, touch, heat, and light are physical inputs. - Smell and taste are chemical input. - Eg: stepping on a hot sand activates sensory neurons in the sole of your feet, which sends a message to your brain, making you aware of the heat so you withdraw your legs. - **Motor Neurons** - This plays a role in movement, including voluntary and involuntary movement. - These neurons allow the brain and Spinal Cord to communicate with the muscle organs and glands all over the body. - There are two types: the lower and upper motor neurons. - **Lower Motor Neuron** - The lower motor neuron carries signals from Spinal Cord to the skeletal or smooth muscle. - **Upper Motor Neuron** - The upper motor neuron carries signals from the brain to the spinal cord. - When one eats, it’s the lower motor neuron which sends a signal to the smooth muscle in the stomach, esophagus, and this muscle contracts, allowing food to move through the stomach to the small intestine. - **Interneurons** - These are neuronal intermediaries found in your brain and Spinal Cord. - They are the most common types and pass signals from sensory neurons to other interneurons and from motor neurons to other interneurons. - Often, they form complex circuits that help you to react to external stimuli. - Example: When you touch something hot, sensory neurons in the fingertip send signals to interneurons in the spinal cord. - Some interneurons have sensory nerves in motor neurons in your hand, which allows you to move the hand. - Other interneurons send a signal to the pain center in your brain and you experience pain. # Topic: Spinal Cord (Neuron Cont...) ### Lecturer: Mr. Ezeugwy ### Date: Fri, 15th Nov 2024. ### Duration: 7:00-9:00 ### The Spinal Cord - The Spinal Cord is the elongated, almost cylindrical part of the CNS, which is suspended in the Vertebral canal. - Surrounded by the meninges and cerebrospinal fluid (CSF). - The spinal cord is continuous above with the medulla oblongata and extends from the upper boarder of the first cervical vertebra atlas to the first lumbar vertebra. - It is approximately 45 cm long in an adult male and about the thickness of the finger. - Except from the cranial nerves, the spinal cord, unlike nervous tissue, links between the brain and the rest of the body. - Nerves conveying impulses from the brain to various organs and tissues descend through the spinal cord. - At the appropriate level, they leave the cord and pass to the structures they supply. - Similarly, sensory nerves from organs and tissues enter and pass upwards in the spinal cord to the brain. - Some of the activities of the spinal cord are independent of the brain and are controlled at the level of the spinal cord by *Spinal Reflexes*. To facilitate this, are extensive neurons connecting between the sensory and the motor neuron at the same or different level in the cord. - The spinal cord is completely divided into two equal parts: - Anteriorly by a short, shallow median fissure and posteriorly by a deep, narrow septum called *posterior median septum*. - A cross-section of the spinal cord shows that it is composed of gray matter in the center surrounded by white matter, which is supported by neuroglial. ### Gray Matter - The arrangement of the gray matter in the Spinal Cord resembles the letter H, having two posterior, two anterior and two lateral colors. - The area of the gray matter lying transversely is the *TRANSVERSE COMMISSURE*, and it is pierced by the central canal and extension from the fourth ventricle containing Cerebrospinal fluid (CSF). - The nerve cell bodies may Sensory neurons, which receives impulses from the periphery, lower motor neurons, which transmit impulses to the skeletal muscle, Connector neurons, also known as Interneurons linking Sensory and motor neurons at the same a different levels, which forms the spinal reflex arcs. - At each point where the nerve impulses are transmitted from the neuron to another, there is a synapse. ### White Matter - The white matter of the spinal cord is arranged in three columns or tracks; anterior, posteriorly, and lateral. - These tracks are formed by: - Sensory nerve fibers ascending to the brain. - Motor nerve fibers descending from the brain, and fibers of *connector neurons*. - Tracks are often named according to their point of origin and destination, eg, *Spinothalamic* (Spinal cord - thalamus) *Corticospinal*. # The Brain ### Cerebrum - This is the largest part of the brain and occupies the anterior and middle cranial fossae. - It is divided by a deep cleft, the *Longitudinal Cerebral fissure*, into the right and left cerebral hemispheres. - Each contains one of the lateral ventricles. - Deep within the brain, the hemispheres are connected by a mass of white, called the *Corpus Callosum*. - The Falx cerebri is formed by the Dura and penetrates to the depth of the Corpus Callosum. - The superficial part of the Cerebrum is composed of nerve cell bodies of gray matter, forming the *Cerebral Cortex*, and the deeper layers consist of nerve fibers or white matter. - The Cerebral Cortex shows many infoldings, or furrows of varying depths. - The exposed areas of the fold are *GYRI* (Con-Volusions), and these are separated by *SULCI*, which are fissures. - This convolution greatly increases the surface area of the Cerebrum. - For descriptive purposes, each hemisphere of the Cerebrum is divided into lobes, which take the name of the bones of the Cranium under, which they lie. - Example: frontal, temporal, parietal, occipital lobe. - The boundaries of the lobe are marked by deep Sulki, these are the central and lateral and the parieto-occipital sulci. ### Diencephalon - This part of the brain connects the Cerebrum on top and the midbrain below. - It consists of several structures situated around the 3rd ventricle, the main ones being the: - **Thalamus** - This consists of two masses of gray and white matter situated within the cerebral hemisphere just below the Corpus Callosum, one on each side of the 3rd ventricle. - Sensory receptors in the skin and visceral send information about touch, pain, and temperature and input from the special sense organs, travel to the thalamus, where there is recognition, although only in a basic form, as refined perception also involves other parts of the brain. - It’s thought to be involved in processing of some emotions and complex reflexes. - The Thalamus relays and redistributes impulses from some parts of the brain to the Cerebral Cortex. - This part of the brain enables one to feel pain where there is pain, be able to recognize objects when the eye is closed. - **Hypothalamus** - This is small and important structure which weighs about 7g and consists of a number of nuclei. - It is situated below and in front of the thalamus, immediately above the pituitary gland. - The hypothalamus is linked to the posterior lobe of the pituitary glands by nerve fibers and to the anterior lobe by complex system of blood vessels through these connections the hypothalamus controls the output of hormones from both lobes of the pituitary glands. - Other functions of the hypothalamus include: - Controls the autonomous nervous system. - Appetite and satiety - Taste and water balance - Body temperature - Emotional reaction (eg pressure, fear, rage) - Sexual behavior and child-rearing - Sleeping and waking cycles ### The Brain Stem #### The Mid Brain - The Midbrain is the area of the brain situated around the cerebral aqueduct, between the Cerebrum above and the pons below. - It consists of nuclei and nerve fibers (tracts) which connects the cerebrum with the lower parts of the brain and the spinal cord. - The nuclei act as the relay stations for the ascending and descending nerve fibers. #### Pons - The pons is situated in front of the Cerebellum below the midbrain and above the medulla oblongata. - It consists mainly of nerve fibers (white matter) that form a bridge between the hemisphere of the Cerebellum and fibers passing between the higher levels of the brain and the Spinal cord. - There are nuclei within the pons that act as the relay stations and some of these are associated with the cranial nerves. - Others form the *pneumotaxic* and *apneustic centers,* that operate in conjunction with the respiratory center in the medulla oblongata. - The anatomic structure of the pons differs from that of the cerebrum in that the cell body (gray matter) lie deeply and the nerve fibers are on the surface. #### The Medulla Oblongata - The Medulla oblongata, or simply the Medulla, extends from the pons above and is continuous with the spinal cord below. - It is about 2 - 5 cm long and lies just within the cranium above the foreman magnum. - Its anterior and posterior surfaces are marked by central fissures. - The outer aspect is composed of white matter, which passes between the brain and the spinal cord to the Cerebrum. - The Vital centers consisting of groups of cell bodies called *nuclei associated with autonomic reflex activity* they lie in It’s deeper structure. - These are : - Cardiovascular center - Respiratory center - Reflex center of Vomiting, Coughing, Sneezing, and Swallowing. #### Reticular Formation - The reticular formation is a connection of neurons in the core of the brain stem surrounded by neural pathways that conduct ascending and descending nerve impulses between the brain and the spinal cord. - It has a vast number of synaptic links with other parts of the brain and is therefore constantly receiving information, been transmitted in the ascending and descending tract. ### Functions of the Reticular Formation - The Reticular formation is involved in: - Coordination of skeletal muscle activities associated with voluntary motor movement and maintenance of balance. - Coordination of activity controlled by the autonomic nervous system (ANS) eg cardiovascular, respiratory, and gastro-intestinal tract activity. - Selective awareness that function through the reticular activity system (RAS) which selectively blocks or passes certain information to the Cerebral cortex. # Topic: Cerebrospinal Fluid (CSF) and Blood Brain Barrier (BBB) ### Lecturer: PHARM. ANOSIKE ### Date: 19/11/2024 (Take note of the nature of the questions!). ### Duration: 8:00-10:00 ## Cerebrospinal Fluid (CSF) - Cerebrospinal fluid (CSF) is similar to some extent to blood plasma and the interstitial fluid. - Like blood, which can be seen in blood vessels, the CSF is seen in the special channel, *Ventricular System*. - It surrounds the entire CNS which includes the brain and spinal cord. - It bath both the internal and external surface of the CNS (brain and spinal cord) and provides a protective cushion. - In a typical adult, the volume of CSF is 150mL. **Question:** What is the volume of CFS in an adult male? **Answer:** 150ml. ## Composition of CSF - The Cerebrospinal fluid is clear, colorless, and slightly alkaline with a specific gravity of 1.005-1.008. - Also, the Cerebrospinal fluid contains inorganic salts (Na, Cl, and traces of proteins and glucose (seen in blood components). ## Difference Between CSF and Blood - While blood has much higher protein content than that of CSF, the glucose level of CSF is just half that of the blood. - Hence, the blood has higher content of protein and glucose than the CSF. - The protein content in the blood, therefore, is much higher in the blood than in CSF, but just twice higher in glucose content. | Component | CSF | Blood/plasma | |---|---|---| | Protein | 25mg/100ml | 600mg/100ml | | Glucose | 50mg/100ml | 100ml/100ml | | Chloride | 120 mEq/L | 100mEq/L | **NB:** Only in chlorine that CSF content exceeds that of the blood. ## Where Is CSF Produced? - About 80% of cerebrospinal fluid is produced in the *choroid plexuses* within the lateral ventricles. - The lateral ventricle is the point where the largest volume of CSF is produced. - The structure responsible for this production is the choroid plexus. *(NB: Not only seen in the lateral ventricle).* - The remaining Cerebrospinal fluid is produced in the choroid plexuses seen in the 3rd and 4th ventricles. - On average adults, about 500mL of CSF is synthesized everyday. - Hence, the body has a high CSF turnover rate compared to 150mL in a normal adult. - When the fluid is filled with metabolites, it is flushed and new one is replaced. ## Function of CSF - It protects the brain and spinal cord from damage/injury. - It supports the brain and spinal cord, helping them to maintain uniform pressure. - The CSF nourishes the CNS. - It is the source of food (glucose, protein) for it. - It helps to maintain steady intracranial fluid volume. - It stabilizes the intracranial volume (Volume of fluid in brain region). - *(NB) When there is brain injury leading to loss of blood, INF mannitol is usually administered to the patient.* - Removes waste products and metabolites from the CNS. - Serves as a pathway for pineal secretion to reach pituitary glands. - Example of this pineal secretion is melatonin, which is responsible for regulating sleep-wake cycle. ## The Blood Brain Barrier (BBB) - This ensures that the brain and spinal cord are selective in what they allow into them. - They play this role through the *tight junction* (space between two adjacent cells). - The barrier protects the brain and the spinal cord from harmful substances like toxic drugs and exogenous substances, that the body considers harmful. - However, gases (oxygen, nutrients) are allowed to pass through them. ## Structure of the Blood Brain Barrier - The Blood brain barrier is made up of: - Endothelial cells - Basement/basal membrane - Astrocytes - Pericytes - Adjacent neurons ## Endothelial Cell - The capillary endothelial cells are found at the interface between the blood and the brain. - They perform essential physiological functions, which include: - Acting as a barrier. - Transport means for micro and macro nutrients to the brain. - Also act as receptor sites. - Responsible for leucocyte trafficking and osmoregulation. ### Components of Endothelial Cell - The structural components of endothelial cell are: - Tight junctions - Adherent junctions - Junctional adhesion molecule/channel #### Adherent Junctions - The adherent junctions are made up of proteins: - Cadherin - Catenin - Vinculin - Actin #### Tight Junctions - These are types of cell junctions characterized by formation of an adhesion complex between two neighboring cells, serving as a tight seal between the cells. - Tight junctions are made up of proteins. - Proteins making up the tightness junctions are: - Occludin - Claudins - Zonula Occludens ## Basement Membrane - This provides structural support for capillary, helping it to interact with the brain tissue. - The types of basement membrane are: - Endothelial basement membrane - Parenchyma basement membrane **Question:** How many types of basement membrane are there? **Answer:** 2 ## Size of Basement Membrane - The basement membrane is made up of highly organized protein with thickness of or within 50-100nm. - They are rich in proteins. - The proteins that make up basement membrane are: - Collagen 4 - Laminin - Nidogen - Pernecan **Question:** Which of the following component is not a protein of the basement membrane? ## Astrocytes - There are clear cells that envelope about 99% of the blood brain barrier endothelium. - Astrocytes are essential for proper neuronal function. - The neurons connect to the astrocytes, which in turn attaches to the BBB. - The astrocytes are located between the neurons and the endothelial cells. - The nerves are seen as nerve glue or cement part of the structure. - They also play a role in sonic hedgehog signaling in the brain, which suppresses expression of inflammatory regulators in the brain endothelial cells. ## Pericytes - The pericytes are flat, undifferentiated, contractile connective tissue that develops at intervals around the capillary wall. **Question:** Which is not a characteristic of pericytes? **NB:** Characteristics of pericytes are flat, undifferentiated, contractile connective tissue, develop at intervals around the capillary wall. - The association of pericytes to blood vessels have been suggested to regulate endothelial cell proliferation, survival, migration, differentiation, and vascular branching. - In the central nervous system, the pericytes are important for blood vessel formation, maintenance of the blood-brain barrier, regulation of immune cell entry into the CNS, and controlling blood brain flow. - Pericytes form part of the neurovascular Unit (NVU). **Question:** In the anatomy of the brain, what does NVU represent? **Answer:** Neurovascular Unit (NVU). - The neurovascular unit (NVU) is a collection of cells that control the interaction between neurons and the cerebral vasculature and meet the energy barrier of the brain. ## Areas of the Brain Devoid of Blood Brain Barrier - The following areas of the brain are devoid of the blood-brain barrier: 1. Pineal Gland 2. Posterior Lobe of the Pituitary Gland 3. Tuber Cinereum 4. Wall of the Supraoptic Vessels of the 3rd Ventricle 5. Area Postrema of the lower end of the floor of the 4th Ventricle. 6. Inferior wall of the Pineal recess 7. Interventricular foramen # Topic: The Meninges ### Lecturer: Mr. Ezeugwy ### Date: 26/11/2024 (Tue) ### Duration: 8:00-9:00 ## The Meninges - The brain and the spinal cord are completely surrounded by three layers or tissues, the meninges, lying between the skull (and the brain) and between the vertebral foramina and the spinal cord. - Named from outside inwards; they are: 1. Dura mater 2. Arachnoid mater 3. Pia mater - The dura and arachnoid mater are separated by a potential space called the *subdural space*. - The arachnoid and pia mater are separated by the *subarachnoid space*, containing the cerebrospinal fluid ie CSF. ## The Dura Mater - The cerebral dura mater consists of two layers of dense fibrous tissue. - The outer layer takes the place of the periosteum on the inner surface of the skull bones, and the inner layer provides protective covering for the brain. - There is only a potential space between the two layers except where the inner layer sweeps towards between the cerebral hemispheres to form the *falx cerebri* - Between the cerebellar hemispheres, to form the *falx cerebelli* and - Between the cerebrum and the cerebellum to form the *tentorium cerebelli*. - Spinal dura mater forms loose sheath round the spinal cord, is extending from the foramen magnum to the second vertebra. - It encloses the filum terminale and fuses with the periosteum of the coccyx. ## Arachnoid Matter - This is a layer of fibrous tissue that lies between the dura and pia mater. - It is separated from the dura mater by the subdural space and forms the pia mater by subarachnoid space containing CSF. - The arachnoid mater passes over the convolutions of the brain and accompanies the under surface layer of the dura mater in the formation of the falx cerebri, tentorium cerebelli. - It continues downward to envelope the spinal cord and ends by merging with the dura mater at the level of the second sacral vertebral. ## Pia Mater - This is a delicate layer of the connective tissue, containing many minute blood vessels. - It adheres to the brain completely covering the convolutions and dipping into its fissures. - It continues downwards and the surrounding spinal cord. - Beyond the end of the spinal cord, it continues as the filum terminale piercing the arachnoid mater and goes on with dura mater to fuse with the periosteum of the coccyx. - The brain contains four irregularly shaped cavities or ventricles, containing cerebrospinal fluid. There are: - The Right and Left Ventricle - The 3rd Ventricle and - The 4th Ventricle ## Lateral Ventricles - This cavity lies within the cerebral hemispheres on each side of the median plane, just below the corpus callosum. - They are separated from each other by a thin membrane, the septum pellicidum and are lined with ciliated epithelium. - They communicate with the 3rd ventricle by the Interventricular foramina. ## The 3rd Ventricle - This cavity is situated between the lateral ventricles, between the two parts of the thalamus. - It communicates with the 4th ventricle by the *cerebral aqueduct*. ## The 4th Ventricle - This is a diamond-shaped cavity, situated between the 3rd ventricle, between the cerebellum and the pons. - It is continuous below the central canal of the spinal cord, communicates with the arachnoid space by foramina in its roof. - The cerebrospinal fluid enters the subarachnoid space through these openings and through the distal ends of the central canal of the spinal cord. ## The CSF - The CSF is secreted into each ventricle of the brain by the choroid plexus. - These are vascular areas where there is a proliferation of the blood vessels, surrounded by ependymal cells in the lining of the ventricular walls. - CSF passes back into the blood through tiny diverticula of the arachnoid matter called the *Arachnoid Villi* (also known as Arachnoid granulations) which project into the venous sinuses. - The movement of the CSF from the subarachnoid space to the venous sinuses depends upon the different in pressure on each side of the wall of the arachnoid villi, which acts as one-way valve. - When the CSF pressure is higher than venous pressure, CSF passes into the blood and when venous pressure is higher, the arachnoid venous collapse, preventing passage of blood constituents into the CSF. - There may also be some reabsorption of CSF by cells on the walls of the ventricles. - From the roof of the 4th ventricle, CSF flows through the foramina into the subarachnoid space and completely surrounds the brain and the spinal cord. - There is no intrinsic system of the CSF circulation, but its movement is aided by pulsating blood vessels respiration, and changes in pressure. - CSF is secreted continuously at a rate of about 0.5ml/min, which is 720ml/day. - The volume remains fairly constant at about 150ml as absorption takes place with secretion. - CSF pressure may be measured using a vertebral tube attached to the lumbar puncture needle inserted into the subarachnoid space above the below the 4th lumbar vertebra, which is below the end of the spinal cord. - The pressure remains fairly constant at about 10cm water when the individual is lying on his back and about 300cm water when sitting up. - If the brain is enlarged, by example, hemorrhage or tumor, some compensations is made by reduction in amount of CSF. - When the volume of the brain tissue is reduced, such as in degeneration or atrophy, the volume of the CSF increases. - CSF is clear, slightly alkaline fluid with a specific gravity of 1.005, consisting of water, mineral salts, glucose, plasma proteins, and small amount of albumin and globulins, creatinine, and urea and few leucocytes.