Midterm Nervous System PDF

The Nervous System  Learning Objective List the functions of Nervous System; List the divisions of the nervous system, and describe the characteristics of each; Describe the structure of neurons and the function of their components. Describe the location, structure, and general functi...

The Nervous System  Learning Objective List the functions of Nervous System; List the divisions of the nervous system, and describe the characteristics of each; Describe the structure of neurons and the function of their components. Describe the location, structure, and general function of glial cells; Define and describe the structure of a nucleus, a ganglion, a nerve tract, and a nerve Learning Objective Compare and contrast the central and peripheral nervous systems Name the two divisions of the autonomic nervous system, and describe the anatomical and neurotransmitter differences between them. Discuss the pathophysiology of diseases associated with the nervous system  Functions Receive sensory output ⚬ Skin, and other organs ⚬ Internal or External Integrate information ⚬ stores information and initiate a response Control muscles and glands Maintaining Homeostasis ⚬ respond to changes in internal and external conditions Establishing and maintaining mental activity ⚬ consciousness, memory, and thinking  Functions Receive sensory output ⚬ Skin, and other organs ⚬ Internal or External Integrate information ⚬ stores information and initiate a response Control muscles and glands Maintaining Homeostasis ⚬ respond to changes in internal and external conditions Establishing and maintaining mental activity ⚬ consciousness, memory, and thinking Division of Nervous System Brain Central Nervous System (CNS) Spinal Cord Nerves to Face Ganglia Peripheral Nervous System Nerves to upper limb (PNS) Nerves to lower limb Division of Nervous System Central Nervous System (CNS) consists of the brain and the spinal cord. Peripheral Nervous System consists of all the nervous tissue outside the CNS, (PNS) including nerves and ganglia. Communication link between the CNS and other parts of the body Subdivided into: a. Sensory Division (Afferent) b. Motor Division (Efferent) Division of Nervous System Peripheral Nervous System (PNS) Sensory Division Motor Division Afferent division Efferent division conduct impulses from the regions conduct impulses from the CNS to various of the body to the CNS regions of the body. Sensory neurons - neurons that Motor neurons - neurons that transmit action transmit action potential from the potential from the CNS to the periphery. periphery to the CNS. Divided into subunits: a. Somatic Nervous System - Skeletal muscle b. Autonomic Nervous System - Cardiac muscle, smooth muscle, and glands  Division of Nervous System Motor neurons (in relation to controlling muscles (voluntary and involuntary) can be further subdivide into: Somatic Nervous System (SNS) – Transmits action potentials from the CNS to the skeletal muscles Autonomic Nervous System (ANS) – Transmits action potentials from the CNS to the cardiac muscles and smooth muscles and glands Division of Nervous System Enteric Nervous System (ENS) unique part of peripheral nervous system contains both sensory and motor neurons found within the digestive tract Cells of the Nervous System 1. Nerve cells (or Neurons) Receive stimuli, conduct action potential, and transmit signals to other neurons or effector organs. Consists of three main parts a. Cell body (soma) - It contains a single nucleus b. Dendrites - short, often highly branching cytoplasmic extensions that are tapered from their bases. It Receive information from other neurons c. Axon - single long process extending from the neuron cell body. ￭ Axon Hillock - area where axon leaves the cell body Cells of the Nervous System 1. Nerve cells (or Neurons) Receive stimuli, conduct action potential, and transmit signals to other neurons or effector organs. Consists of three main parts a. Cell body (soma) - It contains a single nucleus b. Dendrites - short, often highly branching cytoplasmic extensions that are tapered from their bases. It Receive information from other neurons c. Axon - single long process extending from the neuron cell body. ￭ Axon Hillock - area where axon leaves the cell body Cells of the Nervous System Types of Neurons 1. Multipolar neuron ⚬ Contain many dendrites and a single axon. 2.Bipolar Neurons ⚬ Have two processes: one dendrite and one axon 3.Pseudo-unipolar Neurons ⚬ Have a single process extending from the body. ⚬ This process divides into two extensions (1) Extends to the periphery (2) extends to CNS Cells of the Nervous System 2. Glial cells (or Neuroglia) Supportive cells of the CNS and PNS Do not conduct action potential Glial cells are different in the CNS vs PNS a. CNS - (1) Astrocytes, (2) Ependymal Cells, (3) Microglia, and (4) Oligodendrocytes b. PNS - (1) Schwann cells, and (2) Satellite Cells Cells of the Nervous System Astrocytes Major supporting cells in the CNS. Participates with the blood vessel endothelium to form a permeability barrier - Blood- Brain Barrier Cells of the Nervous System Ependymal cells Lines the fluid-filled cavities within the CNS Some ependymal cells produce cerebrospinal fluid. Some has cilia which helps to move the the cerebrospinal fluid through CNS Cells of the Nervous System Microglia Act as an immune cells of the CNS Protect the brain against bacteria and remove cell debris. Cells of the Nervous System Oligodendrocytes Provide insulating material around axons. Cells of the Nervous System Schwann cell Provide insulating material around axons. Cells of the Nervous System Satellite cells Found around the cell bodies of certain neurons of the PNS. Provide support and nutrition to the neurons. Protect the neurons from heavy-metal poisons.  Cells of the nervous system Myelin Sheaths – are specialized layers that wrap around the axons of some neurons These sheaths are formed by the cell processes of glial cells specifically by the oligodendrocytes in the CNS and Schwann cells in the PNS Myelinated axons – Axons with these myelin sheaths Cells of the nervous system Oligodendrocytes and Schwann cells repeatedly wraps around a segment of an axon to form a series of tightly wrapped cell membranes Nodes of Ranvier – gaps in the myelin sheaths, occur about every millimeter between the oligodendrocyte segments or between individual Schwann cells Electrical signals and neural pathways Resting membrane potential In most neurons, the resting membrane potential is around -70 mV (inside of the cell is more negative compared to the outside). The RMP is primarily due to the unequal distribution of ions, such as sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), and negatively charged proteins across the membrane.  Electrical signals and neural pathways Resting membrane potential Potassium leak channels allow K⁺ to move out of the cell, making the inside more negative. The Na⁺/K⁺ ATPase pump actively transports 3 Na⁺ ions out and 2 K⁺ ions in, helping maintain the gradient and the negative charge inside the cell. Electrical signals and neural pathways Resting membrane potential The resting potential is a balance between the chemical gradient (ion concentration difference) and the electrical gradient (charge difference).  Electrical signals and neural pathways Action potential 1. Resting State (Resting Membrane Potential) ⚬ The cell is at rest, with the inside of the cell being more negative than the outside (typically around -70 mV in neurons). ⚬ The sodium (Na⁺) and potassium (K⁺) channels are closed. ⚬ The Na⁺/K⁺ pump maintains the resting potential by moving Na⁺ out and K⁺ into the cell.  Electrical signals and neural pathways Action potential 2. Depolarization A stimulus triggers the opening of voltage-gated Na⁺ channels. Na⁺ ions rush into the cell, driven by both their concentration gradient and electrical gradient. The influx of positive Na⁺ ions causes the inside of the cell to become less negative, leading to depolarization. If the depolarization reaches the threshold potential (typically around -55 mV), an action potential is initiated.  Electrical signals and neural pathways Action potential 3. Rising Phase (Rapid Depolarization) As more Na⁺ channels open, the membrane potential quickly becomes positive (up to around +30 mV). This rapid change in voltage is the peak of the action potential.  Electrical signals and neural pathways Action potential 4. Repolarization Once the membrane potential reaches the peak, voltage-gated Na⁺ channels close. Voltage-gated K⁺ channels open, allowing K⁺ ions to flow out of the cell. The efflux of positive K⁺ ions helps to restore the negative membrane potential.  Electrical signals and neural pathways Action potential 5. Hyperpolarization The K⁺ channels are slow to close, causing more K⁺ to leave the cell than necessary, resulting in a slightly more negative membrane potential than the resting state (below -70 mV). This is called hyperpolarization or the undershoot.  Electrical signals and neural pathways Action potential 6. Return to Resting Potential The voltage-gated K⁺ channels close, and the Na⁺/K⁺ pump gradually restores the resting membrane potential by pumping Na⁺ back out and K⁺ back in. The cell is now ready to respond to another stimulus and generate a new action potential. Electrical signals and neural pathways Action potential conduction 1. Continuous conduction ⚬ occurs in unmyelinated axons ⚬ An action potential in one part of a cell membrane stimulates local currents in adjacent parts of the cell membrane Electrical signals and neural pathways Action potential conduction 1. Saltatory conduction ⚬ Occurs in myelinated axons ⚬ An action potential at one node of Ranvier causes a local current to flow through the surrounding extracellular fluid and through the cytoplasm of the axon to the next node Electrical signals and neural pathways Synapse Junction where the axon of one neuron interacts with the another neuron. Three major components: a. Presynaptic terminal b. Postsynaptic terminal c. Synaptic cleft Division of Nervous System Brain Central Nervous System (CNS) Spinal Cord Nerves to Face Ganglia Peripheral Nervous System Nerves to upper limb (PNS) Nerves to lower limb Spinal Cord Extends from the foramen magnum at the base of the skull to the second lumbar vertebra Cauda equina - Inferior end of the spinal cord Spinal Cord Ascending Tract - axons that conduct action potentials towards the brain Descending Tract - axons that conduct action potential away from the brain Reflex Involuntary reaction in a response to a stimulus applied to periphery and transmitted to CNS Reflex arc - neuronal pathway by which a reflex occurs a. Sensory receptor b. Sensory neuron c. Interneurons d. Motor Neurons e. Effector organ Reflex Knee-Jerk Reflex Also known as the patellar reflex example of a stretch reflex Reflex Withdrawal Reflex Also known as the flexor reflex Remove a limb or another body part from a painful stimulus Painful Stimuli initiate action Receptors conduct action Neurons stimulate muscles to potential potential through dorsal root remove the limb from the stimulus Spinal Nerves Arise along the spinal cord. Contains both sensory and motor neurons (mixed nerves) Dermatomes - area of the skin supplied with sensory innervation by a pair of spinal nerve. Spinal nerves are organized into plexuses: (1. Cervical Plexus; 2. Brachial Plexus; 3. Lumbosacral Plexus) Spinal Nerves Cervical plexus originates from spinal nerves C1 to C4 innervates muscles of hyoid bone, skin of neck, posterior portion of the head Phrenic nerve Spinal Nerves Brachial plexus originates from spinal nerves C5 to T1 Five major nerve emerge from brachial plexus a. Axillary Nerve b. Radial Nerve c. Musculocutaneous nerve d. Ulnar Nerve e. Median Nerve Spinal Nerves Lumbosacral plexus originates from spinal nerves L1 to S4 Four major nerve exit the lumbosacral plexus a. Obturator Nerve b. Femoral Nerve c. Tibial nerve d. Sciatic nerve Brain Stem Connects the spinal cord to the remainder of the brain Control the heart rate, blood pressure, and breathing Consists of three parts a. Medulla Oblongata b. Pons c. Midbrain Brain Stem Medulla Oblongata most inferior portion of the brainstem contains discrete nuclei with specific functions such as regulation of heart rate and blood vessel diameter, breathing, coughing, swallowing, vomiting, sneezing, balance, and coordination. Brain Stem Pons Superior to Medulla oblongata Relay information between cerebrum to cerebellum Its function is similar with the Medulla Oblongata, but it also include chewing and salivation Brain Stem Midbrain Superior to Pons and the smallest region Contains nuclei involved in coordinating eye movements and controlling pupil diameter and lens shape Brain a. Cerebrum Largest part of the brain Divided into left and right hemispheres by a longitudinal fissure Gyri – Numerous folds Sulci – (furrow or ditch/ narrow) Intervening grooves Brain a. Cerebrum Each cerebral hemisphere is divided into lobes Frontal lobe – voluntary motor functions, motivation, aggression, mood and olfactory (Smell) Parietal lobe – principal center for receiving and consciously perceiving most sensory information such as touch, pain, temp, balance. Brain a. Cerebrum Each cerebral hemisphere is divided into lobes Frontal lobe – voluntary motor functions, motivation, aggression, mood and olfactory (Smell) Parietal lobe – principal center for receiving and consciously perceiving most sensory information such as touch, pain, temp, balance. Brain a. Cerebrum Occipital lobe – receiving and perceiving visual input Temporal lobe – involved in olfactory (Smell), auditory (hearing), memory Brain a. Cerebrum Anterior and inferior portion of temporal lobe is called psychic cortex Psychic cortex – responsible for abstract thought and judgement Most of the temporal lobe is separated from the rest of cerebrum separated by a lateral fissure called Insula. Also known as the fifth lobe Brain b. Cerebellum Attached to the brainstem by several large connections called cerebellar peduncles ⚬ Thalamus ￭ Largest part of the diencephalon. It consists of a cluster of nuclei. ￭ Influences mood and registers an unlocalized, uncomfortable perception of pain. Brain b. Cerebellum ⚬ Epithalamus ￭ Small area superior and posterior to the thalamus ￭ Small nuclei - involved in emotional and visceral response to odor ￭ Pineal gland- endocrine gland that influence the onset of puberty. Brain b. Cerebellum ⚬ Hypothalamus ￭ Most inferior part ￭ Plays a central role in the control of body temperature, hunger, and thirst. Sensations such as sexual pleasure, rage, fear, and relaxation Sensory Function CNS constantly receives a variety of stimuli Sensory input to the brainstem and diencephalon helps maintain homeostasis Sensory input to the cerebrum and cerebellum keeps us informed about our environment and allows CNS to control motor function Sensory Function Ascending tracts Spinal cord and brainstem contains a number of ascending tracts Ascending tracts – Pathways that transmit action potential from the periphery to the brain Each tract have different involvement for sensory inputs (pain, temp touch etc.) Sensory Function Names of ascending tract usually begin with prefix “-spino” Indicating they begin in the spinal cord Spinothalamic tract – transmits action potential dealing with pain, and temperature to the thalamus and on to the cerebral cortex Dorsal column – transmits action potentials dealing with touch, position and pressure Sensory Function Spinocerebellar tracts – transmits information about body position to the cerebellum Sensory Function Spinocerebellar tracts – transmits information about body position to the cerebellum Somatic Motor Function Somatic motor system of the brain and spinal cord – is responsible for maintaining the body’s posture and balance As well as, moving the trunk, head limbs, tongue and eyes and communicating through facial expression and speech Other Brain functions Communication between the right and left hemispheres Right cerebral hemisphere – receives sensory input from and controls muscular activity in the left half of the body Left cerebral hemisphere – receives sensory input from and controls muscles in the right half of the body Other Brain functions Commissures (Joining together)– sharing of two hemispheres of the sensory information Corpus callosum – (largest commissures) a broad band of nerve tracts at the base of the longitudinal fissure Other Brain functions Speech The speech area is in the left cerebral cortex(area) Sensory speech area (Wernicke area) – located in the parietal lobe, functions in understanding and formulating coherent speech Motor speech area (Broca’s area) – located in the frontal lobe, functions and controls movements necessary for speech Other Brain functions Memory 1. Working Memory ⚬ information required for the immediate performance of a task ⚬ only lasts for a few seconds to minutes and occurs mostly in frontal cortex. 2. Short-term memory ⚬ last longer than working memory and can be retained for a few minutes to a few days. 3. Long-term memory ⚬ information that become permanent a. Declarative Memory - involves the retention of facts (names, dates, and places) b. Procedural Memory - involves the development of motor skills Other Brain functions Memory Meninges, Ventricles, and Cerebrospinal Fluid Meninges 3 connective tissue membranes Surround and protect the brain and the spinal cord Dura mater – (tough mother) most superficial and thickest of the meninges Dura mater consist of 2 layers (which function as single layer) but are physically separated into several regions to form Dural folds and Dural sinuses Meninges, Ventricles, and Cerebrospinal Fluid Meninges Within the skull, the dura matter adheres tightly to the cranial bones however, there is an epidural space between the dura mater and vertebrae Arachnoid mater (spiderlike as in cobwebs) – second meningeal membrane, it is very thin. Pia mater – third meningeal membrane, is very tightly bound to the surface of the brain and spinal cord Meninges, Ventricles, and Cerebrospinal Fluid Ventricles CNS contains fluid filled cavities called Ventricles Small in some areas and large in some Lateral ventricle – relatively large cavity Third ventricle – is a smaller, midline cavity located in the center of diencephalon Fourth ventricle – is located at the base of the cerebellum and connected to the third ventricle by a narrow canal called cerebral aqueduct Meninges, Ventricles, and Cerebrospinal Fluid Ventricles Cerebrospinal fluid (CSF) Bathes the brain and spinal cord providing protective cushion around CNS Choroid plexuses (lacy) – produce CSF CSF fills the brains ventricles and the spinal cord Autonomic Nervous System Innervates smooth and cardiac muscles and glands (unconsciously) Sympathetic Nervous System – (to fell with, suffering)(flight or fight) Parasympathetic Nervous System – (along side of)(rest and digest) Cranial Nerves 12 pairs of cranial nerves Cranial Nerves 12 pairs of cranial nerves Cranial Nerves 12 pairs of cranial nerves Autonomic Nervous System 12 pairs of cranial nerves Stroke 2 types of stroke a. Ischemic Stroke ￭ Blood clot (thrombus or embolus) obstructs cerebral blood flow. ￭ Brain tissue deprived of oxygen (hypoxia) and glucose. b. Hemorrhagic Stroke ￭ Intracerebral or subarachnoid bleeding. ￭ Direct neuronal damage from blood and pressure. Stroke