what does the nervous system do? what are the key feature of neuron and neuroglia (glial cells0
What it does: provides rapid communication in the body and controls movement, sensation, and internal regulation
Key components
Neurons → conduct signals
Nueroglia (glial cells) → support neurons
CNS vs PNS vs ENS
- CNS
This is the brain + spinal cord and its function is informational processing where it integrates, processes, and coordinates sensory and motor commands - PNS
These are all neural tissue outside the CNS and connects body to CNS - ENS
This is located inside GI tract walls and controls digestion independently
what are the three main parts of a neuron
3 main parts of the neuron:
1. Cell body (soma) → contains then nucleus and is metabolic center
2. Dendrites → receive signals and carry impulses towards the cell body
3. Axon → sends signals away from cell bodies
DENDRITES IN, AXON OUT!
what is an axon hillock, initial segment, axolemma, axoplasm, telodendria, and axon terminals
Axon hillock → where the axon begins and integrates all the incoming signals (origin of axon from cell body)
Initial segment → where the action potential is initiated/starts
Axolemma → axon membrane
Axoplasm → cytoplasm of the axon containing the mitochondria, enzymes, vesicles, neurofibrils
Telodendria → fine branches at end of axon
Axon terminals → release neurotransmitters (aka synaptic terminals)
Which neuron has similar looking processes in terms of axons and dendrites?
Anaxonic neuron — all processes look the same and cannot be distinguished. Found in the brain and special sense organs, function not well understood.
Which neuron has one axon and one dendrite?
Bipolar neuron — has two distinct processes (one axon, one dendrite). Rare, small, and found in special sense organs.
describe unipoalr neuron
Dendrites and axons continuous (fused)
▪ Cell body off to one side
▪ Initial segment is where dendrites
converge
– Remaining part of process is
considered “axon”
▪ Includes most sensory neurons in
peripheral nervous system
– Axons may extend a meter or
more—longest carry sensations from
toes to spinal cord
describe multipolar neuron
▪ Two or more dendrites and
single axon
▪ Most common neurons in CNS
▪ All motor neurons to skeletal
muscles are multipolar
▪ Can be as long as unipolar
neurons—longest carry motor
signals from spinal cord to
muscles that move toes
What are the functional classes of neurons?
Back:
Sensory (afferent) neurons, motor (efferent) neurons, and interneurons.
Which neurons carry information to the CNS and what do they detect?
Sensory (afferent) neurons carry information to the CNS. They detect stimuli through sensory receptors such as interoceptors (internal), proprioceptors (body position), and exteroceptors (external).
What is the difference between somatic and visceral sensory neurons?
Somatic sensory neurons monitor the external environment, while visceral sensory neurons monitor internal body conditions.
Which neurons carry commands from the CNS and what do they control?
Motor (efferent) neurons carry signals from the CNS to effectors like muscles and glands.
What is the difference between somatic and visceral motor neurons?
Somatic motor neurons control skeletal muscles and voluntary movement. Visceral motor neurons are part of the autonomic nervous system (sympathetic and parasympathetic) and control smooth muscle, cardiac muscle, glands, and adipose tissue.
What are interneurons and what are their functions?
Interneurons are found entirely within the CNS and connect sensory and motor neurons. They receive information from both the PNS and CNS and are involved in processing, memory, and learning. theres 20 billion of them
How many neurons do sensory neurons and interneurons have
There are about 10 million sensory neurons and around 20 billion interneurons in the nervous system.
What are neuroglia (glial cells) and what is their general function?
Neuroglia are support cells that protect, support, and assist neurons. They do not conduct nerve impulses.
Which glial cells produce, circulate, and monitor cerebrospinal fluid (CSF)?
Ependymal cells — they line cavities in the CNS and help with CSF production and movement.
Which glial cells act as phagocytes and remove debris and pathogens?
Microglia — mobile immune cells that clean up waste, debris, and pathogens in the CNS.
Which glial cells maintain the blood-brain barrier (BBB)?
Astrocytes — they help isolate the CNS from chemicals in the blood and regulate the environment around neurons. they also absorb and recycle neurotransmitters, and form scar tissue after surgery
Which glial cells regulate ions, nutrients, gases, and recycle neurotransmitters?
Astrocytes — they maintain the chemical balance around neurons and support neuron function.
Which glial cells form scar tissue after injury in the CNS?
Astrocytes — they help repair damage by forming scar tissue.
Which glial cells produce myelin in the CNS?
Oligodendrocytes — they wrap their processes around axons to form the myelin sheath.
What is the function of myelin and which glial cell produces it?
Myelin speeds up nerve impulse transmission by insulating the axon. It is produced by oligodendrocytes in the CNS.
Which PNS glial cells cover peripheral axons and help repair them?
Schwann cells (neurolemmocytes) — they cover axons and participate in axon repair.
