BE 345: Chapter 10

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

• Neurons – transmit impulses

• Neuroglial cells – many other functions

• Central Nervous System (CNS)

• Brain

• Spinal cord

• Peripheral Nervous System (PNS)

• Cranial nerves

• Spinal nerves

Brain

Cranial nerves

Spinal cord

Spinal nerves

Central Nervous System (Brain and Spinal Cord)

Cranial and Spinal nerves

Sensory division and Motor division

Sensory division

Somatic and Autonomic

Skeletal Muscle

Smooth muscle, Cardiac muscle, Glands

Size, shape, length and size of axons and dendrites

Dendrites – receiving ends

• A cell body (soma)– contains nucleus

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

Dendrites

Nucleus

Nucleolus

Chromatophilic Substance

Cell bodies

Axon hillock

Neurofibrils

Impulse

Axon

Nodes of Ranvier

Myelin

Axon

Synaptic knob of axon terminal

Nucleus of Schwann Cell

Portion of a Collateral

Axons which are tightly wrapped by neuroglial cells

• Contains myelinated axons

• Considered fiber tracts

• Contains unmyelinated structures

• Cell bodies, dendrites

Schwann Cell Nucleus

Myelin Sheath

Axon

Neurofibrils

Neurilemma

• 99% of neurons

• Many processes

• Most neurons of CNS

• Two processes

• Eyes, ears, nose

• One process

• Ganglia of PNS

• Sensory

Multipolar neuron

Bipolar neuron

Unipolar neuron

• Afferent

• Carry impulse to CNS

• Most are unipolar

• Some are bipolar

• Link neurons

• Multipolar

• Located in CNS

• Multipolar

• Carry impulses away from CNS

• Carry impulses to effectors

Sensory receptor

Dendrites

Axon (Peripheral Process)

Sensory afferent neuron

Cell body

Axon (Central process)

Cell body

Interneurons

Axon

Axons

Motor (efferent) neuron

Axon terminal

Effector (muscle or gland)

•Scar tissue

• Aid metabolism of certain substances

• Induce synapse formation

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

Myelinating Cell

Myelinating Cell

•Ciliated

• Line central canal of spinal cord

• Line ventricles of brain

Fluid-filled cavity of the brain or spinal cord

Ependymal Cell

Neuron

Astrocyte

Oligodendrocyte

Microglial Cell

Capillary

Schwann Cells, Satellite Cells

• Produce myelin found on peripheral myelinated neurons

• Speed up neurotransmission

• Support clusters of neuron c

• 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.

major intracellular positive ions (cations).

major extracellular positive ions (cations).

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

Gate-like mechanism

Protein

Cell membrane

Fatty acid tail

Phosphate head

a. Channel closed

b. Channel open

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.

•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

Gated ion channels

The membrane potential changes

Hyperpolarized

Depolarized

the greater the stimulus intensity, the greater the potential change

an action potential results

an action potential will not occur

Threshold stimulus

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

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

many voltage gated sodium channels (axon hillock)

Voltage gated Na+ channels open in response to threshold