Functions of the Nervous System

Transcription

1 The Nervous System

2 Functions of the Nervous System 1. Control center for all body activities 2. Responds and adapts to changes that occur both inside and outside the body (Ex: pain, temperature, pregnancy)

3 Anatomy of a Neuron Each neuron contains: - Cell body : The central cell body is the largest part of a neuron and contains the neuron's nucleus. The cell body produces proteins needed for the construction of other parts of the neuron. - Dendrites : fibers that receive messages from other neurons - Axons : fibers that send messages to other neurons - Myelin Sheath : A fatty, axonenwrapping sheath that serves to speed up neural conduction, formed by concentric layers of Schwann's cell

4 Myelin Sheath and Neurilemma:* Formation Marieb 11.5abc

5 Anatomy of a Neuron Neurons do NOT touch; there is a gap between them called a synapse Messages are sent across the synapses by special chemicals called neurotransmitters

6 Two Major Divisions of the Nervous System

7 Central Nervous System Central Nervous System: the complex of nerve tissues that controls the activities of the body. In vertebrates it comprises the brain and spinal cord. Neurons : microscopic nerve cells that make up the brain, spinal cord, and nerves - 30,000 neurons can fit on a pinhead

8 Central Nervous System Brain : a mass of 100 billion neurons located inside the skull -Learning occurs as more and stronger connections are made between neurons

9 Anatomy of the Brain Cerebrum : largest part of human brain - Responsible for: - Thought - Language - Senses - Memory - Voluntary movement

10 Anatomy of the Brain Cerebellum : at base of brain -Responsible for: - Muscle coordination - Balance - Posture

11 Anatomy of the Brain Brain Stem : connects brain to spinal cord -Responsible for: - Breathing - Swallowing - Heartbeat - Blood pressure

12 Central Nervous System Continued Spinal Cord : Column of nerves from brain to tailbone protected by vertebrae of spine - Responsible for: - Conducting impulses between the brain and the rest of the body *Impulses may travel as fast at 268 miles/hr

13 Peripheral Nervous System Nerves : visible bundles of axons and dendrites that extend from the brain and spinal cord to all other parts of the body

14 -Responsibilities: - Sensory nerves - carry messages from body to brain (pain, pressure, temperature) - Motor nerves carry messages from brain to body to respond

15 Peripheral Nervous System: Somatic vs Autonomic Somatic Associated with voluntary control of body movements Skeletal muscles used to do this. Three parts Spinal Nerves Cranial Nerves Association Nerves Autonomic Controls involuntary body functions. Respiration Heart Rate Divided into 2 groups Sympathetic Parasympathetic

16 Divisions of the autonomic nervous system Parasympathetic division Sympathetic division Serve most of the same organs but cause opposing or antagonistic effects Parasysmpathetic: routine maintenance rest &digest Sympathetic: mobilization & increased metabolism fight, flight or fright or fight, flight or freeze 16

17 Parasympathetic Rest and Digest cardiac output: decreases cardiac muscle: Heart rate decreases smooth muscles of bronchioles: contracts pupil of eye: contracts salivary glands: secretions stimulates watery secretions GI tract: increases smooth muscles of GI tract: contracts sphincters of GI tract: relaxes glands of GI tract: secretes

18 Sympathetic Fight, Flight, or Freeze cardiac output: increases cardiac muscle: heart rate increases vascular smooth muscle : Contracts smooth muscles of bronchioles: relaxes pupil of eye: relaxes salivary glands: stimulates viscous smooth muscles of Gastro Intestinal tract: relaxes sphincters of GI tract: contracts glands of GI tract: inhibits

19 Types of Neurotransmitters Marieb 14.2

20 Action Potentials Brief, rapid, large (100mV) changes in membrane potential: potential actually reverses Involves only a small portion of the total excitable cell membrane All or nothing Conduction without decrement

21 Types of Changes in Membrane Potential

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23 Action Potentials When membrane reaches threshold potential Voltage-gated Na+channels in the membrane undergo conformational changes Flow of sodium ions into the ICF reverses the membrane potential from -70 mv to +30 mv Flow of potassium ions into the ECF restores the membrane potential to the resting state Chapter 4 Principles of Neural and Hormonal Communication Human Physiology by Lauralee Sherwood 2010

24 Animation: Nerve cell

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27 Animation: Voltage-gated sodium and potassium channels

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36 Animation: Action potential

37 Action Potentials Additional characteristics Sodium channels open during depolarization by positive feedback. When the sodium channels become inactive, the channels for potassium open. This repolarizes the membrane. An action potential at one point in the plasma membrane regenerates an identical action potential at the next point in the membrane. Therefore, it travels along the plasma membrane undiminished. Chapter 4 Principles of Neural and Hormonal Communication Human Physiology by Lauralee Sherwood 2010

38 Chapter 4 Principles of Neural and Hormonal Communication Human Physiology by Lauralee Sherwood 2010 Action Potentials

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41 Action Potentials Permeability Changes and Ion Fluxes During an Action Potential Figure 4-7

42 Action Potentials Na + /K + pumps gradually restores the concentration gradients disrupted by action potentials. Sodium is pumped into the ECF Potassium is pumped into the ICF

43 Action Potentials are propagated from the Axon Hillock to the Axon terminal

44 Synaptic Cleft: Information Transfer Marieb 11.18

45 The synapse carries a signal from cell to cell

46 Types of Neurotransmitters Marieb 14.2

47 Communication Between Neurons - The use of neurotransmitters causes an electrical current There is enough electrical current in the brain to power a flashlight

48 Problems of the Nervous System Concussion A temporary disturbance of the brain s ability to function due to a hard blow to the head

49 Problems of the Nervous System Paralysis A loss of sensation and movement of part of the body due to an injury of the spinal cord or brain

50 Parkinson s Disease The brain does not produce enough of the neurotransmitter that transmits messages from the brain to the muscles Symptoms: tremors, rigid muscles, shuffling walk, and loss of facial expression Red areas show where chemical is stored

51 Alzheimer s Disease A gradual shrinking of the neurons in the cerebrum Symptoms: memory loss, emotional disturbances, inability to function on own, death

52 Epilepsy Abnormal transmission of messages between the neurons in the brain Symptoms: seizures