Central Nervous System Flashcards
What are the two major functional divisions of the Peripheral Nervous System?
Efferent and Afferent
Efferent includes somatic motor and autonomic; Afferent includes sensory neurons.
What do somatic motor neurons control?
Posture and movement of skeletal muscle
They project to the body wall and limbs.
What do autonomic neurons innervate?
Smooth muscle of organs and cardiac muscle of the heart
Includes gut, glands, lungs, kidneys, and blood vessels.
What is a synapse?
Region of contact between two neurons or a neuron and muscle
What is a presynaptic neuron?
Delivers a signal to the synapse
What is a postsynaptic neuron?
Receives the signal
How do glial cells compare to neurons in number?
Outnumber neurons by 10-50:1
What is the membrane potential?
An electrical potential difference across the cell membrane
What ions are primarily found in extracellular fluid?
Sodium (Na+) & Chloride (Cl-)
What ions are primarily found in intracellular fluid?
Potassium (K+), Phosphate Ions & Negatively charged proteins
What is the resting membrane potential?
The membrane potential at rest when cells are not actively signalling
What are the types of gated channels that control ion permeability?
- Voltage-gated
- Ligand-gated
- Mechanically-gated
What is the function of the NA+/K+ ATPase?
Maintains ionic composition of fluid around cells
What does the NA+/K+ ATPase pump?
3 Na+ out of the cell and 2 K+ into the cell for every ATP hydrolysed
What are graded potentials?
Size of depolarization or hyperpolarization is proportional to stimulus strength
What happens to graded potentials with distance from the site of initiation?
They lose strength due to current leak and resistance
What are subthreshold and suprathreshold signals?
Subthreshold do not initiate action potential; suprathreshold do
What characterizes action potentials?
All-or-None response; no reduction in strength with distance
Where do action potentials usually occur?
At the axon hillock
What is saltatory conduction?
Conduction along myelinated axons that is faster due to less resistance
How does axon myelination in the PNS differ from that in the CNS?
PNS uses Schwann cells; CNS uses oligodendrocytes
What do myelin sheaths give the tissue?
A white color
What is white matter?
Areas of CNS with a high number of myelinated axons
What is gray matter?
Areas of CNS with a high number of cell bodies, dendrites, and unmyelinated axons
What protects the CNS?
Bone, meninges, and cerebrospinal fluid
What are the layers of the meninges?
- Dura mater
- Arachnoid membrane
- Pia mater
What is cerebrospinal fluid (CSF) produced by?
Choroid plexus
What is the function of the blood-brain barrier?
Protects neurons from toxins and harmful substances
Where is the blood-brain barrier present?
Most regions of the brain; absent in some areas like the hypothalamus
What comprises the cerebrum?
Two hemispheres connected by corpus callosum
What are the components of gray matter in the cerebrum?
- Cerebral cortex
- Basal ganglia
- Limbic system
- Amygdala
- Hippocampus
What does the spinal cord contain?
Nuclei with cell bodies of efferent neurons and tracts of axons
What do dorsal roots carry?
Sensory or afferent information to the CNS
What do ventral roots carry?
Motor or efferent information to muscles and glands
