FTHP 112 PPT week 8 UPDATED (1) PDF

Test instructions All books and bags at the front of the room. At your desk, your laptop ONLY – NOTHING ELSE NO CELL PHONES If you have a question, put up your hand and I will come to you. Test is 40 minutes. If you are finished early, you may leave quietly and take a break in the h...

Test instructions All books and bags at the front of the room. At your desk, your laptop ONLY – NOTHING ELSE NO CELL PHONES If you have a question, put up your hand and I will come to you. Test is 40 minutes. If you are finished early, you may leave quietly and take a break in the hallway or quietly at your desk - DO NOT GO FAR – we have lecture afterwards We will start our lecture at 2:30PM The Nervous System Nervous System Classification Structural Classification Central nervous system (CNS) Consists of brain and spinal cord (dorsal body cavity) Act as integrating and command centers Peripheral nervous system (PNS) Consists of nervous system outside of CNS Spinal nerves and cranial nerves Nervous System Classification Functional Classification Sensory (afferent) division Carry information from sensory receptors to CNS Somatic (body) sensory fibers Visceral (organs) sensory fibers Motor (efferent) division Carries impulses from CNS to effector organs (muscles and glands) and cause a motor response Two divisions Somatic (voluntary) nervous system Autonomic (involuntary) nervous system  Nervous System Functions 1. Sensory Input Receives stimulation from sensory receptors Travels in one direction only, to the brain 2. Integration Brain and spinal cord interpret incoming signals Co-ordinate appropriate responses 3. Motor Output Receives stimulation from brain and spinal cord Travel in one direction only, to the muscles, glands & organs  Neuron Anatomy Anatomy Cell body Metabolic center Lacks centrioles (amitotic) Soma Myelin Sheath Protects and insulates fibers and increases transmission rate of impulse In the PNS, myelinated by Schwann cells In the CNS, myelinated by Oligodendrocytes (lacks neurilemma)  Neuron Anatomy Dendrites Carry information towards cell body receive information from other neurons and transmit electrical signals to the cell body. Axons Axons carry information away from cell body – carries the integrated message to the target cell Wrapped in cells known as glial cells (also known as oligodendrocytes and Schwann cells), form the myelin sheath. The myelin sheath which surrounds these neurons has a purpose to insulate and protect the axon. Due to this protection, the speed of transmission to other neurons is a lot faster than the neurons that are unmyelinated. The myelin sheath is made up of broken-up gaps called nodes of Ranvier. Electrical signals are able to jump between the nodes of Ranvier, which helps in speeding up the transmission of signals.  Neuron Anatomy Axon Terminal The end of an axon has an axon terminal that houses specialized cells capable of converting electrical signals into chemical signals for communication with various receptor cells (including muscle cells) Located at the end of the neuron, the axon terminals (terminal buttons) are responsible for transmitting signals to other neurons. At the end of the terminal button is a gap, which is known as a synapse. Terminal buttons hold vessels that contain neurotransmitters. Neurotransmitters are released from the terminal buttons into the synapse and carry signals across the synapse to other neurons. The electrical signals convert to chemical signals during this process. It is then the responsibility of the terminal buttons to reuptake the excess neurotransmitters that did not get passed onto the next neuron.  Functional Classification of Neurons Functional Classification Sensory (afferent) neurons Take nerve impulses from sensory receptors to the CNS Motor (efferent) neurons Take nerve impulses from the CNS to muscles, organs, or glands There are two types of motor neurons: Lower motor neurons – these are neurons that travel from the spinal cord to the muscles of the body. Upper motor neurons – these are neurons that travel between the brain and the spinal cord. Interneurons Highly involved in signal integration Typically located in the CNS  Structural Classification of Neurons Structural Classification Multipolar Most common (99%+ of all neurons in the body) Includes all motor and interneurons Bipolar Rare in adults Only found in some special sense organs (eye, nose) Unipolar (Pseudounipolar) Found in the sensory neurons of the PNS Process functions as an axon  Types of Sensory Receptors Cutaneous Sense Organs Free nerve endings (pain and temperature receptors) Mechanoreceptors Meissner’s corpuscle (touch receptors) Lamellar corpuscle (deep pressure receptors) Thermoreceptor (changes in temperature) Nociceptor (pain receptor) Chemoreceptor (generates biological signal)  Types of Sensory Receptors Proprioceptors Golgi tendon organs (detects changes in tension) Provides information regarding the changes in muscle tension. Lies at the interface between a muscle and its tendon known as the musculotendinous junction also known as the myotendinous junction. Muscle spindle (detect length in muscle) Stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. The responses of muscle spindles to changes in length also play an important role in regulating the contraction  Central Nervous System Components of the CNS Cerebral hemispheres Cerebral Cortex Diencephalon Brain stem Cerebellum  Central Nervous System Functional Anatomy of the Brain Cerebral hemispheres The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. Longitudinal fissure therefore divides the brain into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter, known as the cerebral cortex The Cerebral cortex is supported by an inner layer of white matter. The hemispheres are linked by the corpus callosum, a very large bundle of nerve fibers.  Central Nervous System Grey matter: Area of the brain where actual processing is done Conducts, processes, and sends information to various parts of the body Accounts for approximately 40% of the brain and contains most of the brains neuronal cell bodies. It is fully developed once a person reaches their 20’s.  Basal Nuclei Also referred to as the Basal Ganglia Collection of distinct masses of gray matter lying deep to the white matter tracts Active Selection: the process of choosing between mutually exclusive actions Suppresses movement Prevents more than one movement from occurring simultaneously. Act by modifying ongoing behaviour in motor pathways Regulates muscle tone Influences and regulates muscle movements Inhibits antagonistic and unnecessary movements Monitors and coordinates slow, sustained contractions (especially related to posture and support of the body) Controls large autonomic movements  Diseases of the Basal Nuclei Dysfunctions of this area of the brain can be from many things: Stress, psychological issues, brain damage, or more subtle triggers Symptoms and health conditions you may experience as a result depend on several complex factors such as: Which part of the basal ganglia is affected Whether other parts of the brain are damaged If the whole structure or part of it is over- or under-active Your age, sex, and genetic predispositions Your overall health status  Diseases of the Basal Nuclei Huntington's Disease Hereditary neurodegenerative disorder that usually surfaces in a person’s 30s or 40s. Genetic mutation causes neurons in the basal ganglia that are responsible for muscle movement to die Chorea: involuntary movements affecting all the muscles of the body, specifically the arms and legs, the face and the tongue. Can also can affect the ability to make voluntary movements. Symptoms may include: Involuntary jerking or writhing movements. Muscle rigidity or muscle contracture. Slow or unusual eye movements. Trouble walking or keeping posture and balance. Trouble with speech or swallowing.  Diseases of the Basal Nuclei Parkinson's Disease In Parkinson’s disease, the immune system attacks a group of basal ganglia cells this reduces dopamine release. Blocking impulses from other parts of the brain and therefore making the initiation of movement impossible People with Parkinson’s have trouble beginning a movement. Damage to the basal ganglia explains the hallmark symptoms of Parkinson’s: Tremors Slowness of movement Rigidity Difficulty with balance Movement problems first appear when 30 – 70% of cells in the substantia nigra have died  Central Nervous System White Matter Mainly made up of myelinated axons, also called tracts, which coordinate communication between regions (hemispheres) of the brain and body. Tracts are made up of myelinated never bundles These tracts allow communication between gray matter areas and grey matter areas to the rest of the body Interprets sensory information from various parts of the body Develops through the 20’s and peaks in middle age. Accounts for the other 60% of the brains volume  Corpus Callosum Connective pathway that connects the left to the right side of the brain Sits in the center of the brain Each side of the brain controls movement and feeling in the opposite half of the body. The hemispheres also process information, such as language. Therefore, physical coordination and taking in complex information requires both sides of the brain to work together. The corpus callosum acts as the connector Will form in the brain between 12 and 16 weeks after conception and near the end of the first trimester of pregnancy.  Disease of the Corpus Callosum Multiple Sclerosis (MS) Inflammatory demyelination and axon damage in the corpus callosum are prominent features of MS and may partially account for impaired performance on complex tasks. The immune system attacks the protective sheath (myelin) that covers nerve fibers and causes communication problems between your brain and the rest of your body. Demyelination disrupts the ability of the nervous system to transmit signals, resulting in a range of signs and symptoms, including physical, mental, and sometimes psychiatric problems  Disease of the Corpus Callosum Multiple Sclerosis (MS) As MS lesions can affect any part of the central nervous system, a person with MS can have almost any neurological symptom or sign referable to the central nervous system. Fatigue is one of the most common symptoms of MS. Some 65% of people with MS experience fatigue symptomatology, and of these, some 15–40% report fatigue as their most disabling MS symptom. Autonomic, visual, motor, and sensory problems are also among the most common symptoms.  Central Nervous System Functional Anatomy of the Brain: Cerebral Cortex Outer layer of neural tissue of the brain It is the largest site of neural integration (sensory processing) in the central nervous system Plays a key role in attention, perception, awareness, thought, memory, language, and consciousness. The cerebral cortex is the part of the brain responsible for cognition. The cerebral cortex is folded in a way that allows a large surface area of neural tissue to fit within the confines of the skull This layer has a convoluted appearance with many elevated ridges of tissue called gyri, alternating with grooves called sulci.  Lobes of the Brain Frontal Lobe Largest lobe of the brain comprising almost one-third of the hemispheric surface. Separated from the parietal lobe posteriorly by the central sulcus, and from the temporal lobe posteroinferiorly by the lateral sulcus Functionally, the entire frontal cortex of the frontal lobe is divided into three parts: Prefrontal cortex, motor cortex and Broca’s area.  Frontal Lobe Prefrontal Cortex: It plays a crucial role in the processing of intellectual and emotional information, including aggression, and facilitates judgement and decision-making  Frontal Lobe Motor Cortex: 1. Primary motor cortex: responsible for integrating signals from different brain regions to modulate motor function 2. Premotor area (premotor cortex): functions to assist in organizing movements and actions 3. Supplementary Motor Area: contributes to the control of movement.  Frontal Lobe Broca’s Area Responsible for producing the motor component of speech, which includes verbal fluency, phonological processing, grammar processing and attention during speech.  Lobes of the Brain Parietal Lobe The parietal lobe is located just underneath the parietal bone, lying posterior to the frontal lobe and anterior and superior to the temporal and occipital lobes. The parietal lobe can be divided into three regions 1. Primary Somatosensory cortex 2. Superior Parietal Lobe 3. Inferior Parietal Lobe  Parietal Lobe Primary Somatosensory Cortex Receives sensory information from all sensory receptors that provide information related to: temperature, pain (spinothalamic pathway) vibration, proprioception and fine touch (dorsal column pathway) Thus, this region is mainly involved in processing various types of sensory information.  Parietal Lobe Superior Parietal Lobe: Contributes to sensorimotor integration Inferior Parietal Lobe: Contributes to auditory and language functions Homunculus https://youtu.be/fxZWtc0mYpQ  Lobes of the Brain Temporal Lobe The temporal lobe largely occupies the middle cranial fossa, and its name relates to its proximity to the temporal region/bone of the skull. The temporal lobe is separated from the frontal and parietal lobes superiorly by the lateral sulcus Involved in processing sensory input into derived meanings for the appropriate retention of visual memory, language comprehension, and emotion association.  Lobes of the Brain Occipital Lobe The occipital lobe lies just underneath the occipital bone. It forms the most posterior portion of the brain and is found behind both the parietal and temporal lobes. Is the visual processing hub of your brain. This area processes visual signals and works cooperatively with many other brain areas. It plays a crucial role in language and reading, storing memories, recognizing familiar places and faces, and much more.  Central Nervous System Functional Anatomy of the Brain Diencephalon (interbrain) Thalamus Relay station for sensory impulses Hypothalamus Autonomic nervous system center (homeostatic control) Body temperature, water balance, and metabolism Regulates hormone output of anterior pituitary gland Part of the limbic system (mediates emotional response and involved in memory processing Epithalamus House the pineal gland (endocrine gland) and choroid plexus (forms cerebrospinal fluid)  Central Nervous System Functional Anatomy of the Brain Brain stem Receives lots of internal sensory info: Sounds, sight, touch, blood chemistry, maintains coma state, special senses, visceral sensory system Homeostasis center (efferent): Respiratory , vasoconstriction, heart rate, blood pressure, swallowing, vomiting, coughing, muscle tone, regulates smooth muscle, heart and glands Midbrain Uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons Convey ascending and descending impulses Contains reflex centers involved with vision and hearing  Medulla Oblongata Terminal part of the brainstem located between the pons and spinal cord. Channel for many ascending and descending nerve tracts that carry the information between the brain and spinal cord. Center for vital functions of the body, such as those for the heart rate, blood pressure, and breathing. Innervates the viscera of the head, thorax and abdomen, heart rate and blood pressure regulation (vasomotor center), breathing regulation (respiratory center)  Pons Your pons is a part of your brainstem A structure that links your brain to your spinal cord. It influences your sleep cycle. Your pons sets your body’s level of alertness when you wake up. It manages pain signals. Your pons relays and regulates the signals that give you the sensation of pain from anywhere in your body below your neck. It works with other brain structures. Your pons is a key connection point to your cerebellum, another key part of your brain that handles balance and movement. It also works cooperatively with other parts of your brainstem that manage your breathing.  Central Nervous System Functional Anatomy of the Brain Cerebellum Stands for ‘little brain’ Coordination of voluntary movements Maintenance of balance and posture Refinement of motor skills Motor learning and adaptation Provides precise timing for skeletal muscle activity, helping with fine motor skills and learning new tasks Controls posture and balance through muscle coordination Compares brain’s “intentions” with actual body performance  Cerebellum Primary region responsible for coordinating and refining motor movements, ensuring balance and posture, and facilitating procedural learning. Recent research has expanded our understanding of the cerebellum’s role, suggesting its involvement in cognitive processes, emotion regulation, working memory, attention, and even some aspects of language processing. Thus, in a psychological context, the cerebellum is related to the physical coordination of movements and the coordination of thoughts and emotions.  Protection of the CNS Meninges Protective membranes of the CNS Three layers Dura mater Outer most layer Consists of tough, fibrous connective tissue Arachnoid mater Middle layer Consists of web-like connective tissue filled with fluid Pia mater Deepest layer Allows for water and small solutes to permeate into the brain and provide nourishment  Protection of the CNS Cerebral spinal fluid Forms from blood in the choroid plexuses Similar composition to blood plasma but with less protein and more vitamin C Protects the nervous system tissue from blows and other trauma  Protection of the CNS Ventricles Fluid filled spaces in the brain that make CSF Two lateral ventricles Two central ventricles Peripheral Nervous System Cranial nerves 12 pairs Primarily serve head and neck Exception is vagus nerve which extends to thoracic and abdominal cavities Most are mixed nerves (both sensory and motor in function) Optic, olfactory, and vestibulocochlear are purely sensory in function  Peripheral Nervous System Spinal nerves 31 pairs Named according to the region of the spinal cord from which they arise Mixed nerves Sensory fibers enter at the posterior root Motor fibers exit at the anterior root Divide into dorsal and ventral rami For four large plexuses which serve the motor and sensory needs of the limbs The spinal nerves branch into the dorsal ramus, ventral ramus, the meningeal branches, and the rami communicants.  The dorsal and ventral rami contain nerves that provide visceral motor, somatic motor, and sensory information Dorsal ramus feeding the dorsal trunk (skin and muscles of the back Ventral ramus feeding the ventral trunk and limbs through the ventrolateral surface. The rami communicants contain autonomic nerves that carry visceral motor and sensory information to and from the visceral organs.  Peripheral Nervous System Subdivisions: Sensory (afferent) Somatic sensory Serves the skin, skeletal muscles, joints, and tendons Special senses Visceral sensory supplies the internal organs Motor (efferent) Somatic motor system carries commands from CNS to the skeletal muscles Autonomic motor system regulates cardiac and smooth muscle and glands  Peripheral Nervous System Autonomic Motor Nervous System Two divisions of ANS Function automatically and involuntarily Innervate all internal organs Utilize two motor neurons and one ganglion for each impulse Visceral reflexes Important to the maintenance of homeostasis Control of blood flow, heart and breathing rate, blood pressure, and stomach secretions  Sympathetic vs. Parasympathetic Nervous System The human nervous system is a sprawling network of nerves and cells which, together, regulate several vital functions that take place in our bodies. Sympathetic (SNS) The SNS is the driving force behind the ‘fight or flight’ response and triggers several physiological changes that prepare the body to confront or flee a perceived threat. Parasympathetic (PSNS) The PSNS controls the ‘rest and digest’ functions of the body and maintains the body’s internal environment. It is responsible for regulating digestive and sexual function while keeping heart rate and blood pressure steady. Readings for next week: Chapter 17 Pages 732-738 Review questions