BE 345: Chapter 10

Nervous System

Detects changes, makes decisions, stimulates muscles and glands to respond, and maintains homeostasis

What cell types are in the neural tissue?

• Neurons – transmit impulses

• Neuroglial cells – many other functions

What are the divisions of the nervous system?

• Central Nervous System (CNS)

• Brain

• Spinal cord

• Peripheral Nervous System (PNS)

• Cranial nerves

• Spinal nerves

Label the diagram

Brain

Label the diagram

Cranial nerves

Label the diagram

Spinal cord

Label the diagram

Spinal nerves

Identify the diagram

Central Nervous System (Brain and Spinal Cord)

The Peripheral Nervous System contains what nerves?

Cranial and Spinal nerves

What does the Peripheral Nervous System control?

Sensory division and Motor division

Sensory receptors are in tact with what division?

Sensory division

The Motor division is broken up into what two nervous systems?

Somatic and Autonomic

What does the Somatic Nervous System control?

Skeletal Muscle

What does the Autonomic Nervous System control?

Smooth muscle, Cardiac muscle, Glands

Neurons vary in what?

Size, shape, length and size of axons and dendrites

All neurons contain what?

Dendrites – receiving ends

• A cell body (soma)– contains nucleus

• An axon – transmits impulses and releases neurotransmitters to another neuron or effector

Label the diagram

Dendrites

Label the diagram

Nucleus

Label the diagram

Nucleolus

Label the diagram

Chromatophilic Substance

Label the diagram

Cell bodies

Label the diagram

Axon hillock

Label the diagram

Neurofibrils

Label the diagram

Impulse

Label the diagram

Axon

Label the diagram

Nodes of Ranvier

Label the diagram

Myelin

Label the diagram

Axon

Label the diagram

Synaptic knob of axon terminal

Label the diagram

Nucleus of Schwann Cell

Label the diagram

Portion of a Collateral

What does Myelinated mean?

Axons which are tightly wrapped by neuroglial cells

What does white matter contain?

• Contains myelinated axons

• Considered fiber tracts

What does Grey matter contain?

• Contains unmyelinated structures

• Cell bodies, dendrites

Label the diagram

Schwann Cell Nucleus

Label the diagram

Myelin Sheath

Label the diagram

Axon

Label the diagram

Neurofibrils

Label the diagram

Neurilemma

Multipolar neurons do what?

• 99% of neurons

• Many processes

• Most neurons of CNS

Bipolar neurons do what?

• Two processes

• Eyes, ears, nose

Unipolar neurons do what?

• One process

• Ganglia of PNS

• Sensory

Label the diagram

Multipolar neuron

Label the diagram

Bipolar neuron

Label the diagram

Unipolar neuron

What do Sensory neurons do?

• Afferent

• Carry impulse to CNS

• Most are unipolar

• Some are bipolar

What do Interneurons do?

• Link neurons

• Multipolar

• Located in CNS

What do Motor neurons do?

• Multipolar

• Carry impulses away from CNS

• Carry impulses to effectors

Label the diagram

Sensory receptor

Label the diagram

Dendrites

Label the diagram

Axon (Peripheral Process)

Label the diagram

Sensory afferent neuron

Label the diagram

Cell body

Label the diagram

Axon (Central process)

Label the diagram

Cell body

Label the diagram

Interneurons

Label the diagram

Axon

Label the diagram

Axons

Label the diagram

Motor (efferent) neuron

Label the diagram

Axon terminal

Label the diagram

Effector (muscle or gland)

What do Astrocytes do?

•Scar tissue

• Aid metabolism of certain substances

• Induce synapse formation

• Connect neurons to blood vessels- part of Blood Brain Barrier

What are Oligodendrocytes?

Myelinating Cell

What are Microglia?

Myelinating Cell

What are Ependymal Cells?

•Ciliated

• Line central canal of spinal cord

• Line ventricles of brain

Label the diagram

Fluid-filled cavity of the brain or spinal cord

Label the diagram

Ependymal Cell

Label the diagram

Neuron

Label the diagram

Astrocyte

Label the diagram

Oligodendrocyte

Label the diagram

Microglial Cell

Label the diagram

Capillary

What are the different types of Neuroglial Cells in the PNS?

Schwann Cells, Satellite Cells

Schwann Cells do what?

• Produce myelin found on peripheral myelinated neurons

• Speed up neurotransmission

Satellite Cells do what?

• Support clusters of neuron c

Cell Membrane Potential

• A cell membrane is usually electrically charged, or polarized, so that the inside of the membrane is negatively charged with respect to the outside of the membrane.

• This is as a result of unequal distribution of ions on the inside and the outside of the membrane.

What are Potassium K+ ions?

major intracellular positive ions (cations).

What are Sodium Na+ ions?

major extracellular positive ions (cations).

What are Ion Channels?

formed by membrane proteins, help regulate passage of specific ions into or out of the cell

•Many chemical & electrical factors affect opening & closing of gated channels

Label the diagram

Gate-like mechanism

Label the diagram

Protein

Label the diagram

Cell membrane

Label the diagram

Fatty acid tail

Label the diagram

Phosphate head

Label the diagram

a. Channel closed

b. Channel open

What is a Na+/K+ pump?

transports 3Na+ ions out of cell and 2K+ ions into cell

•The ion distribution is largely created by the Sodium/Potassium Pump (Na+/K+ pump) but also by ion channels in the cell membrane.

What is Resting Membrane Potential (RMP)

•70 mV difference from inside to outside of cell • It is a polarized membrane

• Inside of cell is negative relative to the outside of the cell

• RMP = -70 mV

• Due to distribution of ions inside vs. outside

• Na+ /K+ pump

RMP

Environmental changes can cause what to open?

Gated ion channels

What happens as ions flow through the membrane what happens?

The membrane potential changes

If the membrane potential becomes more negative than the resting potential it is?

Hyperpolarized

If the membrane potential becomes less negative than the resting potential it is?

Depolarized

Local potential changes are graded

the greater the stimulus intensity, the greater the potential change

If degree of depolarization reaches threshold potential of -55 mV what happens?

an action potential results

If degree of depolarization does not reach threshold potential what will happen?

an action potential will not occur

Label the diagram

Threshold stimulus

Label the diagram

Region of depolarization, Na+ channels open, K+ channels closed

Label the diagram

Region of repolarization, K+ channels open, Na+ channels closed

What does the trigger zone at the first end of the axon contain?

many voltage gated sodium channels (axon hillock)

What is the first sequence of events in an action potential?

Voltage gated Na+ channels open in response to threshold