Part 1 Flashcards
What are the functions of the nervous system? (3)
- monitors variables inside and outside the body
- Processes and interprets sensory information
- Generates a response by telling different parts of the body what to do
- glands and muscles = effectors
How is the nervous system organized?
1) Central nervous system: includes the brain and spinal cord
2) Peripheral nervous system: consists of the nerves outside the CNS, including the spinal nerves, which interact with the spinal cord, and cranial nerves, which interact with the brain directly
- the nerves of the PNS are further classified as
a) sensory (afferent) - they convey impulses to the CNS
b) motor (efferent) - they convey impulses from the CNS
Motor neurons can be either voluntary or involuntary
- voluntary nerves make up the somatic nervous system
- involuntary nerves make the autonomic nervous system (ANS)
ANS consists of 2 division that often work complementary with one another
- sympathetic nervous system
- parasympathetic nervous system
What are the two cells in the nervous system?
- Neurons (nerve cells) - excitable cells; most lack centrioles and are long-lined except in adult (nose and hippocampus)
- Neuroglia (glial cells) - supporting cells
Organization of the nervous system: afferent division
Central nervous system: Information processing, integrates, processes, and coordinates sensory input and motor commands
^^^^^
Peripheral nervous system: sensory information within afferent division
^^^^^
Special sensory receptors: monitor smell, taste, vision, balance, and hearing
- receptors
Visceral sensory receptors: monitor internal organs
Somatic sensory receptors: monitor skeletal muscles, joints, and skin surface
Organization of the nervous system: efferent division
Central nervous system: Information processing, integrates, processes, and coordinates sensory input and motor commands
v v v v v
Peripheral nervous system: motor commands within the efferent division
v v v v v
Somatic nervous system (SNS) // Autonomic nervous system (ANS); 2 divisions
v v v v v v v v v v v v v v v
Skeletal muscle Parasympathetic (rest and digest) Sympathetic (fight or flight)
(effectors) v v v v v v v v v v
[ Smooth muscle, cardiac muscle, glands, adipose tissue]
What are the parts of the neuron?
- Cell Body (Soma): Contains the nucleus and organelles, responsible for metabolic functions.
- Dendrites: Receive signals from other neurons.
- Axon: Transmits electrical impulses away from the cell body.
- Axon Terminals: Release neurotransmitters to communicate with other cells.
- Myelin Sheath: Insulates the axon and speeds up electrical signal transmission.
- Node of Ranvier: Gaps in the myelin sheath that facilitate rapid signal transmission via saltatory conduction.
- Nucleus: Houses genetic material and controls the neuron’s activities.
- Neurofibrils: Provide structural support to the neuron.
- Axon Hillock: Initiates the action potential
- Synaptic Terminal: the end of the axon where neurotransmitters are released into the synaptic cleft to communicate with target cells, such as other neurons, muscles, or glands.
What do neurotubules in the axoplasm do?
Use ATP to fast/slow transport vesicles
What is a synapse?
Junction between two neurons that mediates the transfer of information from one neuron and the next
Presynaptic cell: The neuron or cell that sends the signal. It releases neurotransmitters from its synaptic terminal into the synaptic cleft.
Postsynaptic cell: The neuron or target cell (such as a muscle cell or gland) that receives the signal. It contains receptors that bind to the neurotransmitters released from the presynaptic cell, triggering a response.
What is the difference between presynaptic and postsynaptic neurons?
Presynaptic: sends the message
Postsynaptic: receives the message
What happens when neurotransmitters bind to receptors on postsynaptic cell?
- Conveys the signal from presynaptic cell to postsynaptic cell
- Passed on the action potential
What is a unipolar neuron?
Sensory neurons; has a single soma between two axons
What is a multipolar neuron?
Somatic motor neurons; lots of dendrites, soma as dendrites
What is a bipolar neuron?
Rarest, special sense neurons: smell/hearing; cell body in middle connected to dendritic process
What are interneurons?
Neurons that connect motor and sensory neurons to make pathways. Their cell bodies are within the CNS
What are motor neurons?
Neurons that carry signals from the CNS to muscles, viscera or glands. Their cell bodies are located in the CNS
What are sensory neurons?
Neurons that carry signals towards the CNS. Their dendrites are associated with receptors and their somas are located in ganglion outside the CNS
What glial cells are found in the CNS?
Ependymal cells, Astrocytes, Oligodendrocytes, Microglia
What glial cells are found in the PNS?
Schwann cells, Satellite cells
What are ependymal cells?
Simple cuboidal epithelial cells lining ventricles in brain and central canal in spinal cord
- assist in producing, monitoring, and circulating cerebrospinal fluid
What are astrocytes?
Star shaped cells that support neurons by anchoring them to capillaries and protect them from harmful substances. Maintain blood-brain barrier (physically and chemically); provide structural support; regulate ion, nutrient, and dissolved gas concentrations; absorb and recycle neurotransmitters; form scar tissue; role in synaptogenesis during embryogenesis
What are microglia?
Phagocytes that consume debris, bacteria, and dead cells
What are oligodendrocytes?
Myelinate CNS axons, provide structural framework
can provide myelination for 50 axons at a time (bundles them together)
What are satellite cells?
Surround neuron cell bodies in ganglia, regulate O2, CO2, nutrient, and neurotransmitter levels around neurons in ganglia
Protects and cushion in the PNS and regulate exchange of materials between neuronal cell bodies and extracellular fluid
What are schwann cells?
Surround all axons in PNS, responsible for myelination of peripheral axons; participates in repair process after injury
What is the function of myelin?
An insulating sheath around an axon that increases impulse propagation/transmission rate along the axon
What is ganglion?
A collection of neural cell bodies outside the CNS (i.e. in the PNS)
plural - ganglia
What are nuclei?
A collection of neural cell bodies inside the cns
What is an important difference between Schwann cells and oligodendrocytes?
Schwann cells can direct the regrowth of severed axons
Oligodendrocytes cannot; likely due to many axons more involved; astrocyte scar tissue and astrocyte chemical release that blocks axonal regrowth
Consequence: if axons in the brain or spinal cord are severed, the neurons cannot be repaired and paralysis and loss of sensation occurs in region that had been innerveated
Process of schwann cell regrowth of severed axons
- Fragmentation of axon and myelin occurs in distal stump
- Schwann cells form cord, grow into cut, and unite stumps. Macrophages engulf degenerating axon and myelin
- Axon sends buds into network of schwann cells and then starts growing along cord of schwann cells
- Axon continues to grow into distal stump and is enfolded by schwann cells
