Presentation is loading. Please wait.

Presentation is loading. Please wait.

NERVOUS SYSTEM. Introduction Most highly organized system of the body Most highly organized system of the body Fast, complex communication system that.

Similar presentations


Presentation on theme: "NERVOUS SYSTEM. Introduction Most highly organized system of the body Most highly organized system of the body Fast, complex communication system that."— Presentation transcript:

1 NERVOUS SYSTEM

2 Introduction Most highly organized system of the body Most highly organized system of the body Fast, complex communication system that regulates thoughts, emotions, movements, impressions, reasoning, learning, memory, choices Fast, complex communication system that regulates thoughts, emotions, movements, impressions, reasoning, learning, memory, choices Basic Characteristics Basic Characteristics Master control system Master communication system Regulates, maintains homeostasis

3 Major Structures and Divisions Central nervous system (CNS) Central nervous system (CNS) Peripheral nervous system (PNS) Peripheral nervous system (PNS) Automatic Nervous System Automatic Nervous System

4 Functions Monitors change (stimuli) - sensory input Integrates impulses - integration Effects responses - motor output

5 Histology of Nervous Tissue Basic Characteristics Highly cellular 2 types of cells - neurons and supporting cells (neuroglia)

6 Neuroglia Characteristics Dense network of supporting cells for nerve tissue Over 900 billion CAN replace themselves Also known as glia cells (glia = glue) Supportive scaffolding; insulation; neuron health and growth ( act as glue to support, bind, repair, and protect neurons)

7 Neurons: Basic Characteristics Over 100 billion Highly specialized Conduct messages in form of nerve impulses Extreme longevity (>100 years) High metabolic rate 3 functional components in common: receptive/input regions, conducting component/trigger zone, secretory/output component Three types A = afferent (sensory) A = afferent (sensory) C = Connective (associative) C = Connective (associative) E = Efferent (motor) E = Efferent (motor)

8 Neurons: Characteristics Excitability: the ability to react to a stimuli, physical or chemical Irritability: sensory adaptation, with prolonged stimulation, irritability is temporarily lost (i.e. smell) Conductivity: the ability to transmit an impulse Nonmyelinated fibers = meter /sec (1 mph) Nonmyelinated fibers = meter /sec (1 mph) Myelinated fibers = meters/sec (300 mph) Myelinated fibers = meters/sec (300 mph)

9 The Hand as a Neuron

10 A Closer Look: Parts of a Neuron nucleus soma dendrites axon myelin sheath terminal axon

11 Myelin Sheath Whitish, fatty (protein lipoid) segmented covering of axons Myelinated fibers: conduct nerve impulses rapidly; electrical insulation Unmyelinated fibers: conduct impulses slowly White matter: myelinated sheaths around axons of the PNS gives the tissue a white color and forms myelinated nerves (axons = myelinated tracts) Gray matter: concentrations of cell bodies and unmyelinated fibers ( in PNS = ganglia; in CNS = nuclei)

12 NeurophysiologyChemical Events At the Synapse

13 The Synapse the dynamic region between an axon terminal and a receiving neuron space between a terminal axon and receiving neuron is called the synaptic cleft synaptic cleft is where electrochemical transmission takes place, thus communication Impulses from one neuron are transmitted across the synapse to another neuron by a chemical called a neurotransmitter

14 synapse 4 Vesicles release Neurotransmitters

15 Inactivation of Neurotransmitters The action of neurotransmitters can be stopped by four different mechanisms: 1.Diffusion – neurotransmitters drifts away out of synaptic cleft 2. Enzyme deactivation – specific enzyme changes structure of neurotransmitter so it is not recognized by receptor

16 3.Glia cells – astrocytes remove neurotransmitters from synaptic cleft 4. Reuptake – whole neurotransmitter molecule is taken back into axon terminal that released it Inactivation of Neurotransmitters continued

17 Some of the Better Known Neurotransmitters

18 Acetycholine Contributes to movement, learning, memory processes, and REM sleep Only transmitter between motor neurons and voluntary muscles EXCESS: muscle paralysis or convulsions, sometimes death DEFICIT: memory impairment (Alzheimers disease)

19 Dopamine Used by neurons that control voluntary movements Also used by neurons that are important for learning, attention, thought & emotion EXCESS: irrational thought, delusion, and/or hallucinations (Schizophrenia) DEFICIT: tremors, muscular rigidity, (Parkinsons disease)

20 Serotonin Serotonin plays prominent role in regulation of mood, sleep, impulsivity, aggression, and appetite DEFICIT: related to depression, aggressive behavior

21 Norepinephrine Plays a role in eating, sleep, and mood DEFICIT: related to depression

22 Gamma-Aminobutyric Acid (GABA) Appears to have inhibitory effects at synapses Contributes to regulation of anxiety & levels of activity ABNORMALITY in GABA may cause epilepsy

23 Endorphins Opiate-like substances produced in the body Provide relief from pain and produce feelings of pleasure & well-being Drugs such as opium, morphine, and heroin bind with receptors for endorphins Endorphins may explain runners high experienced by long-distance runners

24 Divisions of the Nervous System

25 Central Nervous System – Brain and the Spinal Cord Integrates incoming pieces of sensory information, evaluates the information, and initiates the outgoing responses NO potential for regeneration

26 Brain Largest structure of the nervous system and one of the largest organs of the body 12 billion neurons and neuroglia 12 billion neurons and neuroglia The adult human brain weighs between 1300 g and 1400 g (approximately 3 lbs). A newborn human brain weighs between 350 and 400 g. For comparison: The adult human brain weighs between 1300 g and 1400 g (approximately 3 lbs). A newborn human brain weighs between 350 and 400 g. For comparison: elephant brain = 6,000 g chimpanzee brain = 420 g rhesus monkey brain = 95 g beagle dog brain = 72 g cat brain = 30 g rat brain = 2 g elephant brain = 6,000 g chimpanzee brain = 420 g rhesus monkey brain = 95 g beagle dog brain = 72 g cat brain = 30 g rat brain = 2 g

27 Brain Covered by three layers of membranes called meninges Dura mater Arachnoid Pia mater

28 Structure of the Brain

29 Cerebrum Largest mass of brain (83% of brain mass); uppermost and least protective layer of the brain; responsible for higher mental functions and distribution of impulses Cerebral cortex: outer layer of gray matter; short and long term memory Cerebral medulla: white matter, conduction pathways Divided into right and left hemispheres (left side governs right side of body, right side governs left side of body) Two hemispheres connected by the corpus callosum Each hemisphere has four lobes Middle regions of the cerebrum are canals, called ventricles

30 Right vs. Left Hemisphere Left side processes: Speech Analysis Time Sequence Right side processes: Creativity Patterns Spatial Awareness Context It Recognizes: Letters Numbers Words It Recognizes: Faces Places Objects

31 Lobes Frontal: voluntary motor control, learning, planning, L = motor, speech R = non-verbal abilities. Frontal: voluntary motor control, learning, planning, L = motor, speech R = non-verbal abilities. Parietal: sensory, distance, size, shape, cognitive/intellectual processes Parietal: sensory, distance, size, shape, cognitive/intellectual processes Occipital: vision, visual memory Occipital: vision, visual memory Temporal: auditory, olfactory, speech, judgment, reasoning, will power Temporal: auditory, olfactory, speech, judgment, reasoning, will power

32 Cerebellum Located in the lower back of the cranium; below and posterior to cerebrum Coordinates muscular movement, posture, balance, running, walking Damage produces ataxia (lack of coordination due to errors in speed, force, direction of movement

33 Brainstem (damage = coma) Midbrain: upper part of brainstem * Controls postural reflexes and walking * Visual reflexes and auditory control, 3-4 cranial nerves Pons: (literally means bridge) a two-way conduction pathway that connect the cerebellum and the cerebrum with the rest of the brain, mixed gray and white fibers * Controls inspiration * Transverse fibers give it a bridge appearance * Reflex mediation for 5-8 cranial nerves Medulla oblongata: the bulb (lowest part before the foramen magnum) made of white and gray fibers called reticular formation * 75% of fibers cross here * Controls vital functions: respiration center, cardiac center, and vasomotor center (constricts or dilates the muscles in the blood vessels walls; thus influences BP

34 Diencephalon: area between cerebrum and midbrain Hypothalamus: Regulates autonomic control Cardiovascular control: dilates/constricts Temperature control Controls appetite: hunger and thirst Water balance GI control: peristalsis, intestinal secretions Emotional states: fear, anger, pleasure, pain, sexual reflexes Sleep control Regulates pituitary secretions CHO and fat metabolism Thalamus: gray matter, relay station for sensory incoming and motor outgoing impulses; damage - increased sensitivity to pain, loss of consciousness

35 Spinal Cord Deep grooves: anterior median fissure (deeper) and posterior median sulcus 2 bundles of nerve fibers called roots project from each side of cord Dorsal nerve root: sensory afferent fibers Dorsal root ganglion: sensory cell bodies Ventral nerve root: motor efferent fibers The nerve roots join together to form a single mixed nerve called a spinal nerve

36 Peripheral nervous system (PNS) Made of 12 pairs of cranial nerves and 31 pairs of spinal nerves Afferent (sensory) division Carries impulses toward the CNS Carries impulses toward the CNS Somatic (skin, skeletal muscles, joints) Somatic (skin, skeletal muscles, joints) Visceral (organs within the ventral cavity) Visceral (organs within the ventral cavity) Connecting (associative) neurons Carry impulses from one neuron to another Carry impulses from one neuron to another Efferent (motor) division Somatic: carries information from CNS to skeletal muscles (reflex and voluntary control) Somatic: carries information from CNS to skeletal muscles (reflex and voluntary control)

37 Functions of the Peripheral Nervous System

38 Spinal Nerves 31 pairs of mixed nerves attached to spinal cord by ventral and dorsal roots 8 cervical 12 thoracic, 5 lumbar 5 sacral, 1 coccygeal Each nerve forms several large branches + rami, which subdivide to four complex networks called plexuses (cervical, brachial, lumbar, sacral) Dermatome: mapping of skin surface of nerve intervention

39 The Autonomic Nervous System Sympathetic system The sympathetic nerves are stimulated in situations that require action like the fight-or- flight reaction The sympathetic nerves are stimulated in situations that require action like the fight-or- flight reaction Parasympathetic system The parasympathetic nervous system functions in response to normal everyday situations The parasympathetic nervous system functions in response to normal everyday situations

40


Download ppt "NERVOUS SYSTEM. Introduction Most highly organized system of the body Most highly organized system of the body Fast, complex communication system that."

Similar presentations


Ads by Google