• Functions of Nervous System:

– Sensory Input-(from inside and outside of body)– Integration and regulation of body systems.– Motor output-(Muscles and glands)

• Two Divisions:– Central: Brain and spinal cord.– Peripheral: nerves of body.• Attached to spinal cord.

Motor Neuron

•Multipolar

•Cause muscles to contract or glands to secrete

Sensory Neuron

•Unipolar

•Take signals from a sensory organ to CNS.

•Eyes, ears, pain receptors.

Interneuron•Multipolar

•Only in CNS

•Convey information and coordination of signals.

• Resting Potential

•Polarized membrane- + on outside, - on inside.•Resting potential.•Na/K pump , pumps Na out and K into axon.–Helps keep many more Na on outside and many more K ion inside.

Fig. 8.3a

• Action Potential:– Axon is conducting nerve impulse.

– Axon depolarized: inside becomes + and outside -.• Na moves to the inside.

– Then axon is repolarized: + Out, - Inside.• K moves to the outside,

Fig. 8.3b

• Conduction of Action Potentials:–Myelination helps speed up how fast

nerve impulses can travel through the axon.

•Action potential jumps from node of ranvier to next node of ranvier.

•Called Saltatory conduction.

Fig. 8.4

Fig. 8.5a

Fig. 8.5b

Fig. 8.5c

Brain and CNS

Fig. 8.6b

• Cerebrum:– Largest.– Divided into hemispheres.– Coordinates other parts of the brain.– Center of higher thought processes.• Learning• Memory• Language • Speech

– Divided into 4 lobes:• Occipital, Temporal, Frontal and Parietal

Fig. 8.9

• Diencephenon:– Contains the hypothalamus and thalamus

• Hypothalamus: regulates hunger, thirst, sleep, body temp.–Link between endocrine and nervous systems.

• Thalamus: Memory, emotions and signals to proper part of the brain.

• Pineal Gland: makes melatonin. Regulates body rhythms and biological clock..

• Cerebellum:

–Regulates body posture and balance.

–Regulates smooth body actions.

•Coordinates voluntary movements.

• Plays a huge role in learning new motor skills.

• Brain Stem:– Mid-brain: Relay station.

– Pons: Bridge between cerebellum and rest of CNS and regulates breathing and reflex movement of head.

– Medulla oblingata: Regulates heart rate, breathing, vomiting, coughing, swallowing, etc.

Peripheral Nervous System

• Peripheral nervous system (PNS) is composed of the nerves and ganglia that are outside the CNS.– Nerve: Bundles of myelinated axons.– Ganglia: Swellings associated with nerves that

contain cell bodies.

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• System divided into the somatic and autonomic nervous systems.– Somatic: Serves skin, skeletal muscle and tendons.

Includes sensory neurons.

– Autonomic: Regulates cardiac and smooth muscle.

• Two Types of Nerves:– Cranial: Attached to brain directly.• 12 pairs in humans.

• Most are somatic and control head neck and face.

• Vagus is an exception.: Autonomic and runs to most internal organs.

– Spinal: Attached to spinal cord:• 31 pairs in humans.

• Divided into cervical, thoracic, lumbar and sacral.

• Mixed nerves:– Sensory signals enter via posterior root.

– Motor signals by the anterior root.

Fig. 8.12

Fig. 8.11b

• Somatic Nervous System:–Many actions are voluntary. •Brains tells us to move arm, we send the signal via a somatic motor neuron to move the arm.

–Some actions are involuntary.•Reflexes.

Fig. 8.13

• Autonomic System:– Sympathetic and parasympathetic divisions.–Both function automatically and involuntarily.–Both connect to internal organs.

– Sympathetic: Fight of Flight.•Accelerates heartbeat, dilates bronchi in

lungs, inhibits digestive tract.

– Parasympathetic: Housekeeping.• Promotes food digestion, slows heart rate,

helps body relax.