Chapter 12 Flashcards
CNS
a) components
b) number of neurons
c) functions
a) brain and spinal cord
b) 85 billion neurons in brain, 100 billion neurons in the spinal cord
c) processes sensory information and sends signals for muscles to contract or glands to secrete.
Somatic division of the PNS is composed of what 2 types of neurons?
1) sensory neurons to the CNS from the head, body, and limbs and from receptors of the special sense of visions, hearing, taste, and smell
2) motor neurons that conduct impulses from the CNS to skeletal muscle only (voluntary)
Autonomic division of the PNS is composed of what 2 types of neurons?
1) sensory neurons to the CNS from receptors such as the stomach, heart, and lungs
2) motor neurons from the CNS to smooth muscle, cardiac muscle, and glands (involuntary)
PNS
All nervous tissue outside the CNS: ganglia, enteric plexuses, receptors.
Ganglion
Small masses of nervous tissue outside the CNS but closely associated with the brain and spinal nerves
Enteric plexuses
Networks of neutrons located in the walls of the organs of the gastrointestinal tract which help regulate the digestive system.
ENS
The brain of the gut.
100 million neurons.
Involuntary - propels food through the GI tract
Secretes hormones.
Sympathetic division of the autonomic system
Fight or flight
Parasympathetic division of the autonomic system
Rest and digest
What is contained in the cell body of a neuron?
Nucleus, cytoplasm, organelles
Nissl bodies
Clusters of rough ER - site of ribosomes for protein synthesis - NO protein synthesis in the axon
Dendrite
Nerve finer that emerges from the cell body. Act as the receiver or input portion of a neuron. Multiple and branched.
Axon
Single nerve finer that acts as the output portion towards another neuron, muscle cell, or gland. Contains mitochondria but no rough ER, therefore no protein synthesis
Axon hillock
Where the axon joins the cell body
Initial segment
Their portion of the axon closest to the axon hillock
Trigger zone
Where nerve impulses arise (between the axon hillock and the initial segment).
Synapse
The site of communication between 2 neurons or a neuron and an effector (muscle or gland)
Multipolar: structure and common locations
Several dendrites, single axon. Brain, spinal cord, motor neurons
Bipolar: structure and common locations
Single dendrite, single axon. Eyes, ears, nose
Unipolar: structure and common locations
Dendrites and axon fused together. Sensory receptors for touch, heat, pain
Sensory neurons
Unipolar. Afferent pathways
Motor neurons
Multipolar. Efferent pathways
Interneurons
Mainly in the CNS. Afferent and efferent pathways. Multipolar
2 types of nerve cells
- neuron
2. neuroglia
4 types of neuroglia in the CNS
- astrocyte
- ogliodendrocyte
- microglia
- ependymal
Astrocyte
Neuroglia of the CNS
Largest and most numerous
Support, growth, protection, chemical balance
Ogliodendrocyte
Neuroglia of the CNS
Smaller than astrocyte with fewer processes.
Forms and maintains myelin sheath (lipid/protein coating that insulates and increases speed)
Microglia
Neuroglia of the CNS
Acts as phagocytes, removes debris and repairs damage
Ependymal
Neuroglia of the CNS
Columnar, cuboidal cells that live in the ventricles of the brain and spinal cord that monitor and circulate cerebrospinal fluid.
2 types of neuroglia in the PNS
- Schwann cell
2. satellite cell
Schwann cell
Neuroglia of the PNS
Forms myelin sheath
Participates in axon regeneration
Satellite cell
Free floating neuroglia of the PNS
Provides structure and support
Nucleus vs ganglion
Both are clusters of neuronal cell bodies. Nucleus is in the CNS, ganglia in the PNS
Nerve vs tract
Bundles of axons. Tract in the CNS, nerve in the PNS
Myelin
White in colour. Electrically insulates, and increases speed. Myelin increases through maturity.
Nodes of ranvier
Gaps in the myelin sheath.
Neurolemma
The outer covering of the schwann cell which encloses the myelin sheath. Only in the PNS.
White matter
Primarily composed of myelin. Surrounds grey matter in the spinal cord BUT is surrounded by grey matter in the brain
Grey matter
Unmyelinated portions of tissue: cell bodies, dendrites, neuroglia.
Graded potential
Communication between electrically excitable cells used in short distances
Action potential
Communication between electrically editable cells used in long distances
Leak channel
Randomly alternates between open and closed. Located in nearly all cells: dendrites, cell bodies, axons
Current
The flow of ions exchanges via ion channels
