Download Nervous System PPT 4 - PNS

UNIT B Chapter 12: Nervous System
Section 12.4
The Peripheral Nervous System
• Connection between the central nervous system and the rest of the body.
• Contains the Motor and Sensory pathways.
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UNIT B Chapter 12: Nervous System
Cranial nerves –12 pairs
• Largely concerned with the head, neck, and facial regions
• Vagus nerve (X) branches to internal organs
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Section 12.4
UNIT B Chapter 12: Nervous System
Section 12.4
Spinal Nerves – 31 pairs
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mix of motor and sensory fibres
Dorsal root: sensory fibres that conduct impulses to spinal cord
Dorsal root ganglion: cell bodies of sensory neurons
Ventral root: motor fibres that conduct impulses away from spinal
cord to effectors.
• Each spinal nerve serves a region of the body in which it is located
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UNIT B Chapter 12: Nervous System
Section 12.4
Somatic System – Voluntary and Involuntary
• Voluntary - takes sensory
information from external
sensory receptors to the CNS
and motor commands away
from the CNS to skeletal
muscles
• Serves the skin, skeletal
muscles, and tendons
• Involuntary - Some actions
are due to reflex actions
(automatic responses to a
stimulus)
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A spinal nerve reflex arc
UNIT B Chapter 12: Nervous System
Section 12.4
The Reflex Arc – Reflex involving only Spinal Cord
• Example: withdrawal reflex when touching a sharp object:
• sensory receptors impulse to interneurons in the spinal cord
interneurons signal motor neurons  impulses to skeletal
muscle contracts, giving the response to the stimulus.
• Pain is not felt until the brain receives nerve impulses.
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UNIT B Chapter 12: Nervous System
Section 12.4
Figure 12.13 A somatic reflex arc showing the path of a spinal reflex. A stimulus
(for example, a sharp pin) causes sensory receptors in the skin to generate nerve
impulses that travel in sensory axons to the spinal cord. Interneurons integrate data
from sensory neurons and then relay signals to motor axons. Motor axons convey
nerve impulses from the spinal cord to a sketetal muscle, which contracts. Movement
of the hand away from the pin is the response to the stimulus.
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UNIT B Chapter 12: Nervous System
Section 12.4
Autonomic System
The autonomic system of the PNS regulates the activity of cardiac and
smooth muscle, and glands.
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UNIT B Chapter 12: Nervous System
Section 12.4
Autonomic Nervous System is divided into
Sympathetic and Parasympathetic divisions.
• Both function automatically
• Innervate all internal organs
• For each signal, they use two motor neurons that synapse at
one ganglion
• Involved in reflex actions such as blood pressure and
breathing rate
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UNIT B Chapter 12: Nervous System
Figure 12.14 Autonomic
system structure and
function. Sympathetic
preganglionic fibres (left) arise
from the cervical, thoracic, and
lumbar portions of the spinal
cord. Parasympathetic
preganglionic fibres (right) arise
from the cranial and sacral
portions of the spinal cord. Each
system innervates the same
organs but has contrary effects.
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Section 12.4
UNIT B Chapter 12: Nervous System
Section 12.4
Sympathetic Division: fight or flight” response.
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Increases heartbeat
Dilates pupils
Dilates airways
Shunts blood away from digestive, urinary and reproductive areas
Inhibits salivation
Stimulates liver to release glucose
uses the neurotransmitters epinephrine (adrenaline) and
norepinephrine (NE)
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Sympathetic NS
• Sympathetic ganglia lie near spine
• stress response can feel all encompassing
UNIT B Chapter 12: Nervous System
Section 12.4
Parasympathetic Division: “rest and digest” response.
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Constricts pupils
Stimulates salivation
Decreases heartbeat and blood pressure
Constricts airways
Stimulates gall bladder to release bile
Stimulates digestive tract and urination
Uses the neurotransmitter acetylcholine (ACh), which acts on
different cells to add to the “rest and digest” response
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Parasympathetic Division
• preganglionic neurons have cell bodies located in the
brainstem and in the sacral (toward the bottom) spinal cord
• ganglia often lie near or in effector, not urgent, communicate
only with organs involved.
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Autonomic Nervous System
Which is false?
1. The parasympathetic pathway is responsible for resting the
body, while the sympathetic pathway is responsible for
preparing for an emergency.
2. Most preganglionic neurons in the sympathetic pathway
originate in the spinal cord.
3. Slowing of the heartbeat is a parasympathetic response.
4. Parasympathetic neurons are responsible for releasing
norepinephrine on the target organ, while sympathetic
neurons are responsible for releasing acetylcholine.
Check your progress
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How many pairs of cranial nerves are there?
How many can you list?
How many pairs of spinal cord nerves are there?
What are the divisions of the PNS?
What is the Sympathetic NS responsible for?
Compare effectors of Somatic and Autonomic Systems.
Patellar Reflex Activity
• The patellar reflex is an example of the monosynaptic reflex
arc.
• There is no interneuron in the pathway
leading to contraction of the quadriceps
muscle.
• Instead the bipolar sensory neuron
synapses directly on a motor neuron
in the spinal cord.
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Chapter Summary
The nervous system consists of two types of cells: neurons and
mesoglia.
Neurons are specialized to carry nerve impulses.
A nerve impulse is an electrochemical change that travels along
the length of a neuron fiber.
Transmission of signals between neurons is dependent on
neurotransmitter molecules.
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The central nervous system is made up of the spinal cord and the
brain.
The parts of the brain are specialized for particular functions.
The cerebral cortex contains motor areas, sensory areas, and
association areas that are in communication with each other.
The cerebellum is responsible for maintaining posture; the
brainstem houses reflexes for homeostasis.
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The reticular formation contains fibers that arouse the brain when
active and account for sleep when they are inactive.
The limbic system contains specialized areas that are involved in
higher mental functions and emotional responses.
Long-term memory depends upon association areas that are in
contact with the limbic system.
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There are particular areas in the left hemisphere that are involved
in language and speech.
The peripheral nervous system contains nerves that conduct nerve
impulses toward and away from the central nervous system.
The autonomic nervous system has sympathetic and
parasympathetic divisions with counteracting activities.
Use of psychoactive drugs such as alcohol, nicotine, marijuana,
cocaine, and heroin is detrimental to the body.