human anatomy and phaysiolgy is nervous system fo cranial nerevs, Study notes of Human Physiology

Download human anatomy and phaysiolgy is nervous system fo cranial nerevs and more Study notes Human Physiology in PDF only on Docsity! Organization of Nervous System Have you heard the expression “Information is power?” Nowhere is this truer than in the human body. Without information, we could not survive. Neurons within our nervous system must take in sensory information from the outside world and then decide what to do with the information. Functions of the Nervous System 1. Sensory input – gathering information – To monitor changes occurring inside and outside the body – Changes = are called stimuli 2. Integration – N.S. is able to integrate this information – Process and interpret sensory input and decide if action is needed Functions of the Nervous System 3. Motor output – A response to the integrated stimuli – The response activates muscles or glands The NS does not work alone in maintaining homeostasis. - it enlists the endocrine system for regulating and maintain body functions. The Nervous System • Components – Brain, spinal cord, nerves, sensory receptors • Responsible for – Sensory perceptions, mental activities, stimulating muscle movements, secretions of many glands • Subdivisions – Central nervous system (CNS) – Peripheral nervous system (PNS) Peripheral Nervous System • Two subcategories – Sensory or afferent – Motor or efferent • Divisions – Somatic nervous system – Autonomic nervous system (ANS) » Sympathetic » Parasympathetic » Enteric Nervous System Organization an or display. Stimulus Response (output) (input) — Cardiac muscle, Skeletal — smooth muscle, muscle and glands t PNS Sensory division Somatic Autonomic Sensory conducts action nervous nervous receptors, _ potentials system system nerves, from the \ Motor division / ganglia, periphery conducts action potentials and plexuses lg to the periphery CNS Brain and Processing and y : integrating information, spinal cord initiates responses, mental activity Functional Classification of the Peripheral Nervous System • Sensory (afferent) division - carrying toward a center – Nerve fibers that carry information to the central nervous system – Somatic sensory (skin, skeletal muscle) – Visceral sensory (visceral organs) Organization of the Nervous Central Nervous System (brain and spinal cord) TI Peripheral Nervous System (cranial and spinal nerves) N Nervous Tissue • Comprise of 2 types of cells – Neuroglia = supporting cells • The insulators, adhesive, protectors and nourishers – Neurons = nerve cells that transmit impulses 11-17 Cells of Nervous System • Neurons or nerve cells – Receive stimuli and transmit action potentials – Organization • Cell body or soma • Dendrites: Input • Axons: Output • Neuroglia or glial cells – Support and protect neurons Nervous Tissue: Support Cells • Oligodendrocytes – Produce myelin sheath around nerve fibers in the central nervous system Nervous Tissue: Support Cells (Neuroglia) of PNS • Satellite cells – Surround neuron cell bodies in ganglia, provide support and nutrients • Schwann cells or neurolemmocytes – Wrap around portion of only one axon to form myelin sheath in the peripheral nervous system Neuroglia of PNS Copyright © The McGraw-Hill Companies, Ine. Permission required for reproduction or display. Copyright © The MeGraw-Hil Companies, Ine. Permission required for reproductan o« display Nucleus of Schwann cell Cytoplasm of Schwann cell Myelin sheath Axon Schwann cell Neuron cell body Neuron Anatomy • Cell body – Nissl substance – specialized rough endoplasmic reticulum – Neurofibrils – intermediate cytoskeleton that maintains cell shape Neuron Anatomy 1) poset body ° Cell body oe \ — Nucleus — Large nucleolus ‘Schwann cells, forming the myelin sheath on axon {b) Neuron Anatomy • Extensions outside the cell body – Dendrites – conduct impulses toward the cell body – Axons – conduct impulses away from the cell body Types of Neurons • Functional classification – Sensory or afferent: Action potentials toward CNS – Motor or efferent: Action potentials away from CNS – Interneurons or association neurons: Within CNS from one neuron to another • Structural classification – Multipolar, bipolar, unipolar Functional Classification of Neurons • Sensory (afferent) neurons – Carry impulses from the sensory receptors • Cutaneous sense organs • Proprioceptors – detect stretch or tension • Motor (efferent) neurons – Carry impulses from the central nervous system Functional Classification of Neurons • Interneurons (association neurons) – Found in neural pathways in the central nervous system – Connect sensory and motor neurons Structural Classification of Neurons • Unipolar neurons – have a short single process leaving the cell body Figure 7.8c Functional Properties of Neurons • Irritability – ability to respond to stimuli • Conductivity – ability to transmit an impulse • The plasma membrane at rest is polarized – Fewer positive ions are inside the cell than outside the cell Electrical Signals • Cells produce electrical signals called action potentials • Transfer of information from one part of body to another • Electrical properties result from ionic concentration differences across plasma membrane and permeability of membrane 11-40 Resting Membrane Potential • Characteristics – Number of charged molecules and ions inside and outside cell nearly equal – Concentration of K+ higher inside than outside cell, Na+ higher outside than inside – At equilibrium there is very little movement of K+ or other ions across plasma membrane Changes in Resting Membrane Potential • K+ concentration gradient alterations • K+ membrane permeability changes – Depolarization or hyperpolarization: Potential difference across membrane becomes smaller or less polar – Hyperpolarization: Potential difference becomes greater or more polar • Na+ membrane permeability changes • Changes in Extracellular Ca2+ concentrations 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 Action Potential Copyright © The McGraw-Hill Companies. inc. Permission required for reproduction or display. Na* kt kt diffuse diffuse diffuse = z into | -& out = B out == & = Cn cell = cell = Time Time Time Time Time kK Fane tne 1 . channel cnanne inne channel kt closed opened closed channel kt k* Nat Nat channel Na* Nat channel channel channel K* Kt Kt channel channel channel K* opened kt opened channel + closed Inactivation gate open 14+ Inactivation gate closed Inactivation gate open Activation Activation Activation Activation gate closed gate opened gate opened gate closed 11-45 11-46 Refractory Period • Sensitivity of area to further stimulation decreases for a time • Parts – Absolute • Complete insensitivity exists to another stimulus • From beginning of action potential until near end of repolarization – Relative • A stronger-than- threshold stimulus can initiate another action potential Action Potential Propagation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Outside of membrane becomes | Depolarization more negative as positive charges move away from it GIXOD to — Fett tt +++ Inside of membrane becomes more positive as positive charges move toward it 2 bia LXED tee eee ee —O + tet ts XS ++ +o +, Absolute **** t/*¢ 54 refractory period = Site of TOC ttre prevents another nese *‘ action potential action potential ————& Action potential propagation -47 Continuation of the Nerve Impulse between Neurons • Impulses are able to cross the synapse to another nerve – Neurotransmitter is released from a nerve’s axon terminal – The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter – An action potential is started in the dendrite Axons and Nerve Impulses • Axons end in axonal terminals • Axonal terminals contain vesicles with neurotransmitters • Axonal terminals are separated from the next neuron by a gap – Synaptic cleft – gap between adjacent neurons – Synapse – junction between nerves 11-52 The Synapse • Junction between two cells • Site where action potentials in one cell cause action potentials in another cell • Types – Presynaptic – Postsynaptic 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 Simple Reflex Arc Sensory (afferent) neuron Spinal cord Sensory (afferent) neuron Sensory receptors (pain receptors in the Sensory receptors (stretch receptors in the quadriceps muscle) Synapse in ventral horn gray matter Motor (efferent) neuron Motor (efferent) neuron Effector jomace (biceps (quadriceps brachii muscle of thigh) muscle) say (c) Figure 7.11b—c Types of Reflexes and Regulation • Autonomic reflexes – Smooth muscle regulation – Heart and blood pressure regulation – Regulation of glands – Digestive system regulation • Somatic reflexes – Activation of skeletal muscles Looking at the Brain • The exterior covering (cortex) of the brain is wrinkled which increases the surface area of the brain • The brain is divided into 2 hemispheres – Right and left hemispheres The hemispheres of the brain are connected • The Corpus Callosum connects these hemispheres and allows communication from one side of the brain to the other. Corpus Callosum How are these brains different? ee Bottle-nose ‘G- My JS SAS? id Cres reyatin ) SOS: 2 y yh \ae } yy) a VT 4 f wf : é 4 i SSA x = Y o> >< ay a We ets A PAF Huma eo . _ f . Rat . Rhesus monkey —_——— Chimpanzee ed at) Why are they different? More recently evolved animals have a larger proportion of the brain taken up by the cerebral cortex. The cerebral cortex, made up of four lobes, is involved in many complex brain functions including: ‐memory ‐perceptual awareness ‐"thinking” ‐language and consciousness Does bigger mean smarter? NO… larger brains have nothing to do with intelligence. The Hindbrain • This is the most primitive division of the brain. • The structures in the lower brain tend to be responsible for basic, reflexive functions. • Includes the cerebellum, Pons, and medulla The Hindbrain • The Medulla is the most primitive and lowest portion of the hindbrain (Part of the brain stem). – It controls basic body functions- heart beat, digestion and breathing. Thalamus [sensation] Reticular formation [sleep/wake] Medulla [ “life support” ] Where do complex thought and behavior come from? True or False? We Only Use 10% of Our Brain True or False? We Only Use 10% of Our Brain False! This is a Psychology Myth…we use all of brain most of the time. Forebrain • The Thalamus is a large structure of forebrain that acts a routing station or air- traffic controller. • Processes sensory information from the CNS before it reaches the cerebral cortex • The Hypothalamus is a pea-sized structure that controls many complex behaviors such as eating, drinking and sexual activity. This small structure regulates a variety of complex behaviors. If you have trouble remembering what this structure does try this… The FOUR F’s… It is always good to escape those pesky random battles. Where do my emotions come from? • The limbic system is an interconnected group of structures that are especially significant in emotions, memory, and social behavior. – This is referred to as the “pleasure center” of the brain • The limbic system also includes the hippocampus and amygdala The Limbic System Amygdala Four Lobes of the Brain Frontal Lobe Temporal Lobe Occipital Lobe Parietal Lobe The Occipital Lobe “Eyes in the back of your head” Responsible for vision and visual perception Parietal Lobe • Parietal Lobe is the area that is specialized for the body senses and body image • The parietal lobe is involved with processing information related to: – Touch – Pain – Temperature – Awareness of the location of body parts As you can see from the previous page the amount of cortex that is devoted to each body part is not equally distributed Larger areas are devoted to touch in the most sensitive parts of the body such as lips and hands. Smaller areas are devoted to touch in less sensitive parts of the body such as the back and abdomen. Temporal Lobe • The main processing area for hearing • Is the main processing area for some of the complex aspects of vision – Such as face recognition and motion detection • Involved in aspects of learning, memory, and emotions Frontal Lobe • Includes the Primary Motor Cortex, which controls fine movements such as hand and finger movements • Each area of the primary motor cortex controls a different part of the body – Larger areas are devoted to precise movements of the tongue and fingers – Smaller areas are devoted to movements of the shoulders and elbows