Nervous System Flashcards
Nervous System is divided into:
- Central NS
- Peripheral NS
Define Central Nervous System (CNS)
Body’s coordinating center for mechanical and chemical actions
- made up of brain and spinal cord
Define Peripheral Nervous System (PNS)
- All parts of NS that relay info between CNS and other parts of the body
- Divided into somatic voluntary and autonomic involuntary
PNS consists of:
- Nerves
- Ganglia
- Sensory Receptors
- Effector Organs (muscles and glands)
Define Somatic NS
- Voluntary control (except reflex arc)
- Bring info from external environment to CNS and send info back to skeletal muscle
- send nerves to skeletal muscle,bones n skin
- meditates bodily movement
- composed of 12 pairs of cranial nerves (in brain) and 31 pairs of spinal nerves
- only sensory neurons, motor, or both
Define Autonomic NS
- Involuntary control
- controls organs
- bring info from internal environment to CNS and carries signals back to regulate internal environment
- Controls smooth and cardiac muscle, internal organs and glands
- Motor neurons (pre-ganglia and post-ganglia) stimulate target effectors (muscles,organs)
- Subdivided into : Sympathetic NS and parasympathetic NS
Two types of Nerve cells in NS
- Glial Cell
- Neurons
Define glial cell
- non conducting
- structural support
- metabolism of nerve cells
Define Neurons
- Nerve cells that conduct nerve impulses
- functional units of NS
3 types of Neurons
- Sensory neurons
- Motor neurons
- Interneurons
Define sensory neurons
- Carry impulses (stimuli) from sensory receptors to CNS
- aka afferent (towards) neurons
- Ganglia: collection of sensory nerve cell bodies
Define Ganglia
collections of sensory nerve cell bodies (part of sensory neurons)
Motor neurons
- Carry impulses from CNS to effectors (cell to organ that responds to stimulus)
- aka efferent (away) neurons
Interneurons
- Found in brain and spinal cord
- Link sensory neurons to motor neurons
- Integrate and interpret sensory info and connect to outgoing motor neurons
Dendrites
Projections of cytoplasm that carry impulses towards cell body
Cell bodies
- Contain nucleus
- Receive info from dendrites
Axon
Extension of cytoplasm that carries nerve impulses away from cell body
Myelin Sheath
Insulated covering over axon of nerve cell
Schwann Cell
Special type of glial cell that produces the myelin sheath
Nodes of Ranvier
- Reoccuring gaps between sections of myelin sheath along axon
- Nerve impulses jump from node to node
- Speeds up nerve transmission
Neurilemma
- Delicate membrane surrounding axons within PNS ONLY
- formed by schwann cells
- promotes regeneration of damaged axons
- not all myelinated cells contain neurilemma
What is the speed of an impulse dependent on?
- Myelin
- Diameter of axon: Bigger = faster
Myelin
Myelinated axon send impulses faster than non-myelinated axons bcs impulse jumps from node to node along axon
White Matter
Nerves within brain that contain myelinated fibres
- called white matter bcs myelinated axons are whitish in appearance
Grey matter
- Other nerve cells in brain and spinal cord, lack myelin sheath
Grey and white matter
Cells of grey and white matter in CNS lack neurilemmas, causing damages to CNS to be permanent.
Define Reflex Arc
- simplest nerve pathway
- neural circuit thru spinal cord
- reflexes involuntary & unconscious (no brain coordination)
Essential components for reflex arc
- Receptor
- Sensory neuron
- Interneuron (in spinal cord)
- Motor neuron
- Effector
Sympathetic NS
- Prepares body for stress
- Nerves come from ribs and small of back
Parasympathetic NS
- reverse effect of sympathetic NS and restores body to normal
- Nerves exit from brain,neck, or tailbone
- Contains Vagus Nerve: branches of nerve supply nerves to the heart, bronchi of lungs, liver, pancreas, and digestive tract
Flight or Fight
- Sympathetic NS activated > stress response > u escape, fight or flight
- requires intense muscular effort
