Ch.12 Nervous system

Somatic nervous system

From CNS to skeletal muscle (voluntary)

Autonomic nervous system (ANS)

From CNS to smooth muscle, cardiac muscle, and certain glands; divisions: sympathetic, parasympathetic, and enteric; two neuron system

Sympathetic

Prepares body for physical activity

Parasympathetic

Regulates resting or vegetative functions (digesting food, emptying urinary bladder)

Choroid plexus

Within certain regions of ventricles; secretes CSF

Microglia

Specialized macrophages; responds to inflammation, phagocytize necrotic tissue, microorganisms, and foreign substances, and foreign substances that invade CNS

Oligodendrocytes

Form myelin sheaths if surrounding axon; single cells can form myelin sheaths around portions of several axons

Schwann cells, neurolemmocytes

Wrap around portion of only one axon to form myelin sheath, wrapping many times; cell membrane, primarily phospholipid

Satellite cells

Surround neuron cell bodies in sensory ganglia; provide support and nutrients

Gated ion channels

Open and close because of a stimulus; when open, they change cell membrane permeability

Ligand-gated

Open or close in response to ligand such as ACh binding to receptor or glycoprotein

Voltage-gated ion channels

Open or close in response to small voltage changes across the cell membrane

Depolarization

Voltage shift to less negative value

Resting membrane potential

Voltage gated Na+ and K+ channels are closed (activation gates are closed and inactivation gates are open)

Action potential phases

Resting membrane potential, depolarization, depolarization, threshold potential

All or none principle

No matter now strong the stimulus, as long as it is greater than the threshold, then action potentico will occur and the neuron fires up to maximum voltage

Repolarization

Voltage - gated Na+ channels are closed because the inactivation gates close; voltage - gated K+ channels are now open

One of repolarization and after - potential

Voltage - gated Na+ channels are closed

Resting membrane potential

Reestablished after the voltage - gated K+ channels close

Non-decremental

Doesn't get weaker with distance

Irreversible

If a neuron reaches threshold, the action potential goes to completion and can't be stopped

Action potential

All or none, non decrementeul, irreversible

Neuromodulators

Adjust or modulate the activity of neuron groups in various ways (increasing the release, adjusting the sensitivity, altering the neurotransmitter reuptake or breakdown)

Parkinson disease

Progressive loss of motor function due so degeneration of dopamine releasing neurons in a portion of the brainstem called the substantial nigra

Synaptic plasticity

Ability of synapses to change

Synaptic facilitation

Making it easier to transmit signals across a synapse

Long term potentiation

Molecular changes in synapse remodeling