1. Nervous System

2. Nervous System: Neurons
Neurons are masses of nerve cells that transmit information to other nerves, tissues or cells (nerve impulses). Consists of
1. cell body- contains the nucleus and two extensions.
2. dendrites- shorter, more numerous, receive information. (carry to the cell body)
3. Axons- single, long
fiber which conducts
impulses away from
the cell body.

3. There are two parts to the nervous system:
Central nervous system (CNS)
Consists of the brain and spinal cord
Peripheral Nervous System (PNS)
Includes 31 pairs of spinal nerves
Includes 12 pairs of cranial nerves

4. Functions of the Nervous System
1. Sensory Function- gathers information within and around the body, sends nerve impulses to the CNS.
2. Integrative function- information is interpreted, to create sensations, create thoughts, add to memory, make decisions, etc.
3. Motor Function- responds to signals (impulses). Signals go from the CNS to effectors (muscles or glands).

5. Brain Integration center of the body
Constant input from sensory organs
Constant learning
Memory of response or outcome
Huge collection of myelinated and unmyelinated neurons
Divided into lobes: different sensory and motor functions are controlled by different lobes.

6. Brain Three major parts:
Cerebrum: largest, sensory and motor functions, higher mental function (memory, reasoning)
Cerebellum- coordinate voluntary muscles
Brain stem- regulate visceral functions

7. Brain Sulci and gyri are along the surface Sulci are shallow grooves
Gyri are ridges or bumps
Fissures are deep grooves

8. Brain

10. Parietal lobe: input lobe
Major sensory lobe
Hard drive/memory
Speech understanding-Broca’s area
Recognition of people, places, items, events, etc.
Memory of outcomes
taste

11. More lobes: Occipital lobe: Temporal lobe: Cerebellum:
Receives input from the eyes and sends it to the parietal lobe for interpretation
Temporal lobe:
receives input from the ears and sends it to the parietal lobe for interpretation
memory processing –short term
Cerebellum:
fine motor coordination
balance and posture
*increases its control with practice

12. Brain stem 1. midbrain: 2. pons: 3. medulla oblongata:
auditory and visual reflexes
eye movement
fluidity of movement
2. pons:
integration center for cerebellum and cerebral communication
respiratory center
3. medulla oblongata:
involuntary muscle control
autonomic reflexes
respiratory/cardiovascular center
vomiting, coughing, hiccupping, sneezing, swallowing

13. Nervous system division

14. Cells of the nervous System: Neurons
The neuron:
Large, complex cells
Longevity: long life
Lack centrioles- cannot perform mitosis
Classified by structure and function

15. Parts of a neuron
Cell body: contains the nucleus and all other cellular organelles along with the bulk of cytoplasm
Dendrites: receptive or input regions that provide enormous surface area for receiving signals from receptor organs/glands
Axon: in each neuron, there is only one! It can be very long or so short it seems nonexistent. Conduction component that generates and propagates nerve impulses away from the cell body.

16. More parts of a neuron….
Myelin: fatty covering that insulates the axon. Gaps between myelin are called nodes of Ranvier.
2-4 mph without myelin
250 mph with myelin
Axon terminal: end of the axon where neurotransmitters are stored and released.

17. Functional classification of a neuron (how it reacts in the body)
Sensory: receive impulses and transmit to the brain
-afferent neurons
Motor: receive impulses from the brain and send them to effector organs
-efferent neurons
Interneuron: communicate between motor and sensory along the spinal cord
-association neurons

18. Structural Classification of a neuron
Multipolar: 3 or more attachments to the cell body
*** most common structure
Bipolar: 2 attachments to the cell body
*** rare- special senses
Unipolar: 1 attachment to the cell body
*** rare- PNS sensations

19. Cells of the nervous System: Neuroglial Cells
Supportive tissue of the nervous system (more numerous than neurons) 5 types:
Microglial cells
Oligodendrites
Astrocytes
Ependymal cells
Schwann cells

20. More neuroglia: Oligodendrocyte: in CNS Ependymal: In CNS
Branching cells
Wrap their branches around the neuron’s axon insulating it with myelin
Ependymal: In CNS
Epithelial cells
Produce and form a barrier between neurons and CSF

21. Neuroglia Astrocyte –in CNS Microglia- in CNS Small, branching cell
Most abundant neuroglia
Braces neurons to capillaries- exchanges between neurons and capillaries
Microglia- in CNS
Thorny cells
Monitors neuron health

22. More neuroglia: Satellite Cell: in PNS Schwann Cell: in PNS
Looks like moons or satellites
Job is still unknown but thought to act as astrocytes
Schwann Cell: in PNS
Has branching extensions like oligodendrocytes
Wraps its branches around PNS neuron axons to insulate them with myelin

24. Nerve impulses
Nerve impulse: propagation of an impulse from dendrite to axon terminal
Resting membrane potential: high concentration of sodium ions outside the membrane and a high concentration of potassium inside the cell.
Na/K channel vs Na/K
pump: channels are
open and allow ions to
flow freely while pumps
turn off and on to reset
the membrane potential

25. Depolarization:
neuron membrane is more permeable to sodium ions.
* Na+ flows into the neuron
Repolarization: neuron membrane is more permeable to potassium ions.
*K+ flows out of the neuron
Hyperpolarization: too much potassium leaves making the neuron too negative
~ -90mV
After hyperpolarization,- sodium/potassium pumps reset the resting membrane potential.