Physiology & Pathophysiology (Nervous System) Fall 2023 Galala University PDF

F A C U L T Y O F P h a r m a c y F A L L 2 0 2 3  1 Physiology & Pathophysiology (Nervous system) Dr. Ramadan Saad  Objectives: 1 Explain the difference between the c...

F A C U L T Y O F P h a r m a c y F A L L 2 0 2 3  1 Physiology & Pathophysiology (Nervous system) Dr. Ramadan Saad  Objectives: 1 Explain the difference between the central and the peripheral nervous system. 2 Describe the functions of the nervous system. 3 Describe the structure of a neuron. 4 Describe the structure and function of a synapse. 5 Describe the function of the blood-brain barrier. 6 Describe functions of meninges. 7 Describe the functions of the spinal cord. 8 List the major divisions of the brain and give the general functions of each. 9 Explain the two divisions of the autonomic nervous system. 3  Introduction ❑Nervous system is a highly ❑Controls all other organs complex system divided systems and is important for into two major parts; maintaining balance within ❑ Central nervous system (CNS) those systems. ❑Peripheral nervous system. Disorders of the nervous system are numerous and often very difficult to diagnose and treat because of the complexity of this system. 4 Organization of the Nervous System 6  Functions of the Nervous System 1. Sensory input – gathering information To monitor changes occurring inside and outside the body (changes = stimuli) 2. Integration to process and interpret sensory input and decide if action is needed. 3. Motor output A response to integrated stimuli The response activates muscles or glands  Functional Classification of the Peripheral Nervous System Sensory (afferent) Motor (efferent) division Motor (efferent) division division Two subdivisions Nerve fibers that carry Somatic nervous system = Nerve fibers that carry impulses away from the voluntary information to the central nervous system Autonomic nervous central nervous system system = involuntary  Spinal Cord - Ascending and Descending Tracts ❑ Function of the spinal cord is to carry information to and from the brain ❑ Ascending tracts: carry sensory information up to the brain ❑ Descending tracts: carry motor information down from the brain to muscles and glands 9  - Apply Your Knowledge Answer What do the descending tracts of the spinal cord do? Descending tracts carry motor information down from the brain to muscles and glands 10  The Brain Four Parts: ❑ Cerebrum ❑ Diencephalons ❑ Brain stem ❑ Cerebellum  Functions of The Cerebrum This is the largest part of Frontal Lobe Parietal Lobe the brain. personality Concerned with Each cerebral hemisphere receiving is composed of different lobes; frontal, temporal, sensations ( parietal and occipital. touch,  Frontal lobe; Influences temperature, the personality of the pressure, and person.  Parietal lobe; This is the pain). principal center for the reception and Occipital Lobe interpretation of Concerned Sensation. visual  Occipital lobe; sense of vision. information Temporal Lobe  Temporal lobe; senses of smell and sound. Governs hearing, smell.  Layers of the Cerebrum Basal ganglia – internal islands of gray matter Regulates voluntary motor activities Dysfunction of this part of the brain = unable to control muscles, rigidity, ant tremors. (Parkinson’s Disease)  The Cerebellum The cerebellum is located at the back of the brain. Functions Coordinates gait Maintains posture, equilibrium Controls voluntary muscle activity Damage to this area in humans results in a loss in the ability to control fine movements, maintain posture, and motor learning The most common cause of cerebellar dysfunction is alcohol poisoning, but also trauma, tumors, and stroke 15  The Brainstem It is composed of the midbrain (A), the pons (B) and the medulla oblongata (C). Functions: has the center for respiration and cardiovascular system.  The Diencephalon (The thalamus and the hypothalamus) The thalamus is the relay station of all sensory stimuli towards the brain. The hypothalamus Controls body temperature, appetite, body fluids, and endocrine functions.  Limbic system Series of structures: functions in learning and memory and elicits emotional responses (i.e. pain, pleasure, affection, anger).  Cerebrospinal Fluid Function: Location: subarachnoid space around the brain and Spinal Support, protect, & Cord. exchange of materials Formed by the choroid Forms a watery cushion to plexus protect the brain Circulates to monitor levels of CO2, O2 , pH – triggers feedback mechanism if necessary  Blood Brain Barrier Includes the least permeable capillaries of the body Excludes many potentially harmful substances Useless against some substances Fats and fat-soluble molecules Respiratory gases Alcohol Nicotine Anesthesia Apply Your Knowledge The patient has had trauma to the pons of the brain. What type of problems would you see in the patient? 21  - Apply Your Knowledge Answer The patient has had trauma to the pons of the brain. What type of problems would you see in the patient? The patient could not breath without assistance. 22  The SYNAPSE This is the region where communication occurs between 2 neurons or between a neuron and a target cell A neurotransmitter is released from the nerve cell towards the other cell with receptor  TRANSMISSION OF CHEMICAL SIGNALS ACROSS THE SYNAPSE Presynaptic membrane Postsynaptic membrane [plasma membrane of the cell body or dendrite of a neighbouring Synaptic terminal neurone] Synaptic cleft Receptor Axon mitochondria Dendrite Direction of transmission of Synaptic vesicle nerves impulses The binding of the When an electrical impulse reaches The neurotransmitters bind to the neurotransmitters to the the end of first neuron, → release receptors in the second neuron receptors leads to the neurotransmitters generation of new electrical signal The Autonomic Nervous System The part of the peripheral nervous system that innervates cardiac muscles, smooth muscles and glands Functionally divided into; Sympathetic Nervous System Parasympathetic Nervous System  Prepares the body for stressful situations or an emergency, in which the Sympathetic responses are associated with ‘fight or flight’. Increases the pulse rate, and blood pressure. division Slows down the digestive system so that more blood is available to carry oxygen to the vital organs such as the brain, heart and muscles. Neurotransmitters are Epinephrine and Norepinephrine. ADRENERGIC system. Associated with a relaxed state Decreases the pulse rate, and blood pressure. Parasympathetic Stimulates the digestive system to continue breaking down division food. Neurotransmitter is Acetylcholine. CHOLINERGIC system.  Nerve Physiology The nerve cells are excitable cells. Any stimulus will change the membrane potential → impulse or action potential. The myelin sheath of the nerve cell → increases the velocity of nerve transmission.  Starting a Nerve Impulse Depolarization – a stimulus depolarizes the neuron’s membrane A deploarized membrane allows sodium (Na+) to flow inside the membrane The exchange of ions initiates an action potential in the neuron  The Action Potential If the action potential (nerve impulse) starts, it is propagated over the entire axon Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane The sodium-potassium pump restores the original configuration This action requires ATP  Action potential (nerve impulse)  Depolarization; Na+ pass into the neuron.  Repolarization; at this point, K+ pass out of the neuron.  Return to resting membrane potential: by closure of K channels and activation of Na-K pump. A local anaesthetic works by blocking the sodium channels in nerves from the affected part of your body, so that they cannot transmit pain signals to your brain. Nerve Impulse Propagation Impulses travel faster when fibers have a myelin sheath. In Multiple Sclerosis, the myelin sheath is destroyed. This is considered an autoimmune disease.  The Reflex Arc Reflex – rapid, predictable, and involuntary responses to stimuli Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector  Traumatic Brain Injuries Concussion Slight brain injury No permanent brain damage Contusion Nervous tissue destruction occurs Nervous tissue does not regenerate Cerebral edema Swelling from the inflammatory response May compress and kill brain tissue  Cerebrovascular Accident (CVA) Commonly called a stroke The result of a ruptured blood vessel or obstructed vessels by clot supplying a region of the brain Brain tissue supplied with oxygen from that blood source dies Loss of some functions or death may result  Alzheimer’s Disease Progressive degenerative brain disease Mostly seen in the elderly, but may begin in middle age Structural changes in the brain include abnormal protein deposits within neurons Victims experience memory loss, irritability, confusion and ultimately, hallucinations and death  Classification of sensation A. General sensations: (a) Superficial (touch spots, heat spots, cold spots) (b) Deep (c) Visceral (it is sensitized only under abnormal conditions) B. Special senses: (a) Taste (b) Smell (c) Vision (d) Hearing Pain  Why feel pain? “Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” Gives conscious awareness of tissue damage Protection: Remove body from danger Promote healing by preventing further damage Avoid noxious stimuli 1Nociceptors Nociceptors are special receptors that respond only to noxious stimuli and generate nerve impulses which the brain interprets as "pain". Fast pain (acute) ◦occurs rapidly after stimuli (0.1 second) ◦sharp pain like needle puncture or cut ◦not felt in deeper tissues ◦Transmitted to the brain by type A (myelinated)nerve fibers  Slow pain (chronic) ◦Begins more slowly & increases in intensity ◦in both superficial and deeper tissues ◦smaller C nerve fibers ◦Transmitted to the brain by slowly C nerve fibers (unmyelinated). Visceral pain Often accompanied by strong autonomic and/or somatic reflexes Poorly localized; may be “referred” Mostly caused by distension of hollow organs or ischemia (localized mechanical trauma may be painless)  Referred pain Pain originating from organs perceived as coming from skin Site of pain may be distant from organ E.g. Pain of heart to left shoulder Pain from gall bladder to right shoulder. Faculty of Nursing 44