Nerve Tissue (lec 16) Flashcards
Organization of the nervous system
Divided into 2 systems:
CNS (brain and spinal cord)
PNS (cranial nerves and spinal nerves)
3 sub categories of PNS (peripheral NS)
- somatic nervous sys. (SNS)
- autonomic nervous sys. (ANS)
- enteric nervous system (ENS)
What does the Somatic Nervous System (SNS) do? [part of PNS]
Transmits Signals:
- Sensory: related to external stimuli from receptors in skin, muscles, joints, special sense organs
- Motor: to skeletal muscles
What does the Autonomic Nervous System (ANS) do? [part of PNS]
Transmits signals:
- Sensory: related to internal stimuli from receptors in visceral organs/tissue
- Motor: to cardiac muscle, smooth muscle and glands that are located in the viscera of the body
Neuroglia of the peripheral nervous system
- Satellite cells
- create supportive framework & regulate composition of interstitial fluid
- functionally similar to astrocytes
- Schwann cells
- produces myelin
- functionally similar to oligodendrocytes
Neuroglia of the central nervous system
- Astrocytes (star shaped)
- main support cell
- guide neuron development
- maintain the blood-brain barrier
- Oligodendrocytes
- cells that produce myelin
- Ependymal cells
- line the canals and ventricular and produce Cerebrospinal Fluid (CSF) - Microglia
- migrate around CNS & removes cellular debris & pathogens
What does the Enteric Nervous System (ENS) do? [part of PNS]
Transmits signals:
Sensory: internal stimuli (G.I Tract)
Motor: GI tract
2 types of cells nervous tissue consists of
Neuoglia (support cells that provide structure to nervous system)
- smaller but more abundant than neurons
Neurons (functional unit cells that transmit signals around the body)
EXAM INFO: Neuroglia
Will not need to label neuroglia’s of CNS on a diagram for final exam
What is Myelin
Fatty substance wrapped around Axons of some neurons.
- protects axon
- increases conduction speed of Axon
What is white matter
Region of myelinated axons
What is grey matter
region of unmyelinated axons / neuronal cell bodies.
Parts of a neuron
- Cell Body
- expanded portion that contains the typical cell bits
- Dendrites (input)
- branched structures that transmit signals in response to stimuli toward cell body
- Axon (output)
- single long branch extending out from cell body that transmits action potentials away from cell body & toward axon terminals (only one way)
- Axon terminals (transmit signals to a neuron/ effector cell [muscle cell or gland cell])
What is a cluster of cell bodies in the CNS called?
Nucleus
What is a cluster of cell bodies in the PNS called?
Ganglion
What is a bundle of axons in the CNS called
Tract
What is a bundle of axons in the PNS called?
Nerve
Axon transmits it’s signals in how many directions?
One - away from cell body
Structural classification of Neurons
Multipolar
(Many dendrites and one axon extend out from cell body) [most common]
Bipolar
(One dendrite and one axon extend out from cell body) [special sense organs I.e. eye, ear]
Unipolar
(Dendrites and axon are fused) [ sensory neurons of PNS]
What are the 3 functional classifications of neurons?
Sensory neurons
Motor neurons
Interneurons
What do Sensory neurons do
- Transmit sensory signals from peripheral receptors to the CNS
What do motor neurons do?
Transmit signals from the CNS to the peripheral effectors (muscle cells, gland cells)
What do interneurons do?
- transmit signals between sensory and motor neurons
- Contained entirely in the CNS
Generation and propagation of electrical signals in neurons
All cells have a ____________ generated by differences in the levels of positive and negative ions located inside and outside the cell.
resting membrane potential
Neurons and muscle cells are unique in that their membrane potential can change in response to _________.
External stimuli
In neurons membrane potential changes are classified as:
Graded potentials - (generated/transmitted in dendrites and cell bodies)
Action potentials - (generated/transmitted in axons)
What are graded potentials?
- Vary in magnitude
- Small changes in small area of cell membrane that diminish in magnitude as they travel along the cell membrane (similar to ripples from when object falls into water)
- can be excitatory (more positive) of inhibitory (more negative - further from threshold)
- can undergo spatial and temporal summation (add together effects of graded potentials - net effect)
What are action potentials?
- Constant magnitude as it travels along cell membrane
- Large change in the cell membrane potential
- always excitatory (become more positive - closer to threshold)
- cannot undergo summation
What is this process called:
when an action potential travels down an axon to an axon terminal it is transmitted to another neuron across a small space called a synapse.
signal propogation between neurons
What are the two types of synapse transmissions?
Electrical - direct transmission via small connecting channels
Chemical - indirect transmission via release of neurotransmitters
excitatory meaning
produces a graded potential that brings the neuron’s cell membrane closer to threshold
- if cell membrane reaches threshold - action potential is generated in neurons axon
inhibitory meaning
produces a graded potential that brings the neuron’s cell membrane further from threshold
