Chapter 12-Intro to Nervous System Flashcards
Rapid, specific signals cause ___ responses by the body.
Immediate
3 Overlapping functions of the nervous system
Sensory input, integration, motor output
Sensory Receptors
Monitor changes inside and outside body
CNS
Receives and interprets sensory input
Effector organs
Motor neurons elicit responses using effector organs
Central Nervous System
Brain and Spinal chord, functioning in integration and command
Peripheral Nervous System
Divided into somatic and autonomic systems, functioning in communication
Afferent
Towards
Efferent
Away
Somatic
Areas outside of ventral body cavity e.g. skin, skeletal musculature, bones,
Visceral
Structures in the ventral cavity e.g. digestive tubes, lungs, heart, bladder
Somatic Sensory
touch, pain, pressure, vibration, temp, hearing, equilibrium, vision
Visceral sensory
Taste, smell, stretch, pain, temperature, chem changes, irritation of viscera, nausea, and hunger
Somatic motor
motor innervation to skeletal muscles
visceral motor (autonomic nervous system)
motor innervation to smooth muscle, cardiac muscle and glands (involuntary)
Nervous tissue is made of
neurons and neuroglia
neuroglia
nonexcitable supporting cells that surround and wrap the neurons
Characteristics of neurons
- Conduct electrical Signals- able to send electrical signals from one body part to another
- extreme longevity- last a lifetime (typically)
- do not divide- cannot be replaced
- high metabolic rate- require constant supply of O2 and nutrients
Parts and Functions of a Neuron
Dendrites- processes that extend from the cell body acting as receptive sites for signal recognition
Cell body- single nucleus surrounded by cytoplasm and is the focal point for the outgrowth of neuron processes
Axon- arising from the axon hillock, a neuron process which ends in terminal boutons and covered by schwann cells that act as impulse generators and conductors
Structural Classification of Neurons
- Know difference between dendrites and axon in multipolar
- Know difference between fused dendrite and axon in bipolar
- know difference between the peripheral and central processes which comprise an axon in unipolar (psuedounipolar)
Functional Classification of Neurons
grouped according to direction nerve impulse travels relative to CNS
Sensory Neurons
(afferent neurons) towards the CNS
Motor Neurons
(efferent neurons) away from the CNS
Association Neurons
Interneurons- within the CNS
Axodendritic synapse
neuron-neuron synapse
axosomatic synapses
neuron-cell body synapse
Neuroglia
Support cells
Types of CNS Neuroglia
Astrocytes, Microglia, Ependymal cells, Oligodendricytes
Types of PNS neuroglia
Satellite Cells, Schwann cells
Astrocyte
( attaches to capillaries) Most abundant CNS neuroglia
Microglial Cells
(attaches to neurons) Defensive Cells in the CNS
Ependymal Cells
(look like teeth with cilia) line cerebrospinal fluid-filled cavities
Oligodendrocytes
processes which form myelin sheaths around CNS nerve fibers
Satellite cells
cover neuronal cell bodies in the PNS
Schwann cells
form myelin sheaths in the PNS
Schwann cell vs. oligodendricyte
Schwann cells wrap around 1 axon of 1 neuron in PNS whereas Oligodendricyte can wrap around many axons of many neurons in the CNS
Myelin
multilayered lipoprotein structure that wraps pieces of axons
- electrical inulation
- speeds rate of action potential
- Schwann cells in PNS
- Oligodendricytes in CNS
Nodes of Ranvier
Gaps in myelin Sheath
Neurilemma
the outer, nucleated, cytoplasmic layer of the schwann cell… outermost layer of myelin sheath
Myelinated Axon (PNS)
schwann cell wraps several times around an axon
Unmyelinated Axon (PNS)
Schwann cell surrounds and encircles many axons
Neurilemma Function (PNS vs CNS)
- When Axons are damaged in PNS, neurilemma forms a regeneration tube which acts as a tunnel
- This does not happen in the CNS because oligodendricytes do not forma neurilemma
Grey matter vs white matter
Grey matter (where cell bodies are clustered) surounds white matter (consist of axons running between different parts of CNS) in the brain whereas white matter surrounds grey matter in the spinal cord
What is a ganglion?
Cluster of soma in the PNS
What is a nerve?
Cluster of axons in the PNS
What is a nucleus?
Cluster of soma in the CNS
What is a tract?
Cluster of axons in the CNS
Nerves in the PNS are…
cable-like organs in the PNS; many parallel axons arranged in bundles called fascicles; within each nerve, each axon is covered by Schwann cells (myelinated and unmyelinated axons)
3 layers of CT in the PNS
Endoneurium- CT surrounding the Schwann Cells
Perineum- CT surrounding fascicles
Epineurium- CT surrounding an entire nerve
- each axon is surrounded by Schwann cell, then covered by CT
Reflex
Rapid, automatic, motor responses to stimuli
Reflex arc
simple chain of neurons that cause reflexes
Monosynaptic Reflexes
No interneuron, one synapse
Stretch reflex
Polysynaptic Reflex
Multiple interneurons, multiple synapses Withdrawal reflex (pain withdrawal), activates flexor muscles ex. bicep flexes, tricep must be relaxed neuron also inhibits antagonist muscle