Chapter 11: The Nervous System And Nervous Tissue Flashcards
What does the CNS consist of?
Brain and Spinal Cord
What are the anatomical subdivisions of the PNS?
- Cranial Nerves (12 pairs, carry impulses to and from the brain)
- Spinal Nerves (31 pairs, carry impulses to and from the spinal cord)
What are the functional subdivisions of the PNS?
-Sensory (afferent) division (tells the CNS what is happening both inside and outside of the body)
Includes: Somatic sensory neurons (carry impulses to skin, skeletal muscles) and visceral sensory neurons (carry impulses to visceral organs)
-Motor (efferent) division (conducts impulses from CNS to effector organs, specifically muscles and glands)
Includes: Somatic Nervous System (voluntary nervous system) and Autonomic Nervous System (involuntary)
What are the subdivisions of the Autonomic Nervous System (ANS)?
This is your involuntary nervous system
- Sympathetic (fight or flight, exercise/emergency actions) example: increase heartbeat & respiratory rate, dilate pupils
- Parasympathetic (rest and digest response) example: decrease heartbeat & respiratory rate, constrict pupils.
What is the difference between Afferent and Efferent and where do their impulses travel?
Afferent (sensory) nerves convey impulses from the sensory receptors in the skin, muscles and joints to the CNS while
Efferent (motor) nerves carry impulses from the CNS out to the muscle glands
What are the two groups or types of cells that make up nervous tissue?
- Neurons (nerve cells) electrically excitable cells that respond to stimulus and convert it into Action Potential (an electrical signal)
- Supporting Cells (neuroglia) these are supportive cells that help nourish and protect the neurons
What are Oligodendrocytes?
Cells that wrap the CNS axons to form myelin sheaths.
(Myelin serves to insulate the axon electrically and help increase speed at which impulses travel)
The areas of axon covered by myelin sheath are called internodes, the small gaps in between are called nodes (of Ranvier)
What are Schwann cells?
Similar to oligodendrocytes but they form myelinated and unmyelinated sheaths over all of the axons of the PNS.
Schwann cells also play a role in regeneration of damaged nerve fibers.
What is the difference between Oligodendrocytes and Schwann Cells?
Oligodendrocytes= Central Nervous System
Schwann Cells= Peripheral Nervous System
What are the three parts of a neuron and their functions?
- Cell body= contains the nucleus and other organelles (a.k.a Soma)
- Dendrites= Processes that receive signals and transfer them to the cell body. Transferred via short distance electric signals called graded potentials.
- Axon= A single process that generates and transmits an action potential (AP) to another nerve, muscle, or gland.
What is the difference between gray and white matter?
White matter is myelinated
Gray matter is unmyelinated
What is the purpose of myelination? What is node of Ranvier? What is an internode?
Myelination is a covering that surrounds most nerve axons to electrically insulate them and increase speed through which a neuron can transmit an action potential down its axon
Internodes are the areas of the axon that are wrapped in a myelin sheath
Nodes of Ranvier are the gaps between each internode
What is the difference between a graded potential and an action potential?
Graded potentials are used for SHORT distance (ex: sending an impulse from a dendrite to the cell body) A strong enough gradient can trigger an axon to form an action potential.
Action potentials are used for LONG distance communication. Travels through CNS and PNS, triggering the release of a neurotransmitter when the neuron synapses at another nueron, muscle, or gland.
What is the resting membrane potential? What unit is it measured in?
The electrical potential difference across the plasma membrane when the cell is in a non-excited state. It is measured in millivolts.
What does the concept of a threshold refer to?
The critical level to which a membrane potential must be depolarized to initiate an action potential.
For example: An Action potential occurs when a neuron sends information down an axon, away from the cell body. When the depolarization reaches about -55mV, a neuron will fire an action potential. If the neuron does not reach this critical threshold level, then no action potential will fire.
