Bio Lecture 9 Flashcards
_______– all neurons have the ability to respond to environmental changes
Excitability
________– Neurons produce traveling electrical signals that quickly reach other cells at distant locations
Conductivity
________– when the electrical signal reaches the end of a nerve fiber, the neuron usually secretes a chemical called a neurotransmitter that stimulates the next cell
Secretion
__________ neurons – neurons specialized to detect stimuli such as light, temperature, or pressure and to transmit information about them towards the CNS
Sensory (afferent)
________ (association neurons) – neurons located entirely within the brain or spinal cord
Interneurons
These neurons carry out the integrative function of the nervous system – they process, store and retrieve information, and “make decisions” about how the body responds to stimuli
_________
Interneurons
________ (efferent) neurons – neurons that send signals to muscle or gland cells, sending signals away from the central nervous system
Motor
_____ (cell body) – control center of the neuron
Has a nucleus and cytoplasm containing organelles like other cells
Soma
________- processes of a neuron that receives information from other cells or from environmental stimuli
It conducts signals toward the soma
________ are usually shorter, more branched, and more numerous than the axon
Dendrites
_____ – process of a neuron that conducts action potentials away from the soma
Each neuron has only one ____
Axon
The _____ end of an axon usually has termina arborization
Terminal arborization is an extensive complex of fine branches
distal
Each branch ends in a _______ _____ (terminal button)
Swollen tip of the distal end of an axon; the site of synaptic vesicles and neurotransmitter release
synaptic knob
_______ neurons – Have one axon and two or more dendrites
This type is common in the brain and spinal cord
Multipolar
______ neurons – have one axon and one dendrite
Includes olfactory cells and sensory cells of the inner ear
Bipolar
______ neurons – have only one process leading away from the soma
Also called pseudounipolar neurons
Includes neurons that carry signals to the spinal cord
Unipolar
_______ neurons – have multiple dendrites but no axon
This type is found in the brain and retina
Anaxonic
__________ – Forms a myelin sheath around nerve fibers in the central nervous system
Oligodendrocytes
_________ – form the blood-brain barrier that controls which substances are able to get from the bloodstream into the brain tissue
Astrocytes
________ Cells – produce cerebrospinal fluid and help to circulate cerebrospinal fluid
Ependymal
_______– develop from white blood cells and phagocytize dead nervous tissue, microorganisms, and other foreign matter
Microglia
________ Cells – envelop peripheral nervous system fibers with myelin and assist in the regeneration of damaged fibers
Schwann
Insulating layer around a nerve fiber
Formed by oligodendrocytes in the CNS and Schwann cells in the PNS
_________
Myelin
Axons are covered in segments
Gaps between segments are called nodes of Ranvier
Myelin-covered areas between nodes of Ranvier are called internodes
Axons are covered in segments
Gaps between segments are called nodes of Ranvier
Myelin-covered areas between nodes of Ranvier are called internodes
In an unmyelinated nerve fiber, the signal spreads by diffusion of sodium and potassium ions through the plasma membrane at every point along the fiber
The ion movement creates a sudden voltage change called an action potential at each point
Each action potential triggers another one just ahead of it
The nerve signal consists of a wave of action potentials traveling down the axon
This signal travels at about .5 to 2 m/sec
In a myelinated nerve fiber, the ion movements through the membrane occur only at the ____ __ _______ (gaps between segments of myelin)
nodes of Ranvier
In the _______ (myelin covered portions), signals travel by a much faster process of ion diffusion along the length of the nerve fiber immediately under the plasma membrane
the signal can travel as fast as 120 m/sec
internodes
________– the meetings between neurons and any other cells
Synapses
________ _______ – junctions in which the presynaptic neuron releases a neurotransmitter to stimulate the postsynaptic cell
Chemical synapses
At a chemical synapse, a terminal branch of a presynaptic fiber ends in a swelling called the synaptic knob
Between the synaptic knob and the next cell there is a 20-40 nm gap called the synaptic cleft
A nerve signal arrives at the end of the presynaptic neuron and triggers the release of neurotransmitters that either excite or inhibit the postsynaptic cell
______ ________ – junctions in which adjacent cells are joined by gap junctions
Ions diffuse directly from one cell to the next for quick transmission
Electrical synapses
________– the spinal cord contains fibers that conduct information up and down the body
It enables sensory information to reach the brain
It enables motor commands to reach the receptors
Input received at one level of the spinal cord can affect output at another level
Conduction
_________– the simple repetitive muscle contractions that put one foot in front of another are controlled by central pattern generators in the spinal cord
The spinal cord does not control the speed or direction of locomotion (those are under control of the motor neurons in the brain)
Locomotion
________– the spinal cord is responsible for involuntary stereotyped responses to stimuli
Reflexes
31 pairs of spinal nerves over five regions
8 Cervical (C1-C8)
12 Thoracic (T1-T12)
5 Lumbar (L1-L5)
5 Sacral (S1-S5)
1 Coccygeal
31 pairs of spinal nerves over five regions
8 Cervical (C1-C8)
12 Thoracic (T1-T12)
5 Lumbar (L1-L5)
5 Sacral (S1-S5)
1 Coccygeal
The diameter of the spinal cord is relatively constant except for the cervical enlargement and lumbar enlargement
The diameter of the spinal cord is relatively constant except for the cervical enlargement and lumbar enlargement
________ ___________
Location in which the cord tapers to a point below the lumbar enlargement
Conus medullaris
______ _______
Bundle of nerves resembling a horse’s tail that innervates the pelvic organs and lower limbs
Cauda equina
___ _______ – outermost meninx that forms a dural sheath around the spinal cord
Dura mater
______ space is found between the sheath and the vertebral bone
- It is a space filled with blood vessels, loose connective tissue, and adipose tissue
- It is a site where anesthetics are sometime introduced to block pain signals
Epidural
______- middle meninx that adheres to the inside of the dura mater composed of a loose mesh of collagenous and elastic fibers
Arachnoid
___________ space is the gap between the arachnoid and the pia mater
Filled with cerebrospinal fluid
Subarachnoid
________ _______ is a (subarachnoid) space occupied by the cauda equina below the medullary cone
Lumbar cistern
___ ______ – innermost layer of the meninges that closely follows the contours of the spinal cord
Pia mater
____ matter – has a dull color because it contains very little myelin
Contains the somas, dendrites, and proximal parts of the axons of neurons
Gray
______ matter – has a pearly white color because it contain myelin
Composed of axons that carry signals from one part of the CNS to another
White
Spinal Tracts: (2)
Ascending tracts
Descending tracts
_____– cordlike organ composed of axons bound together by connective tissue
Nerve
_____ nerve – consists of both sensory and motor fibers and transmits signals in two directions (but any one fiber transmits in only one direction)
Mixed
______ nerve – consists of sensory axons, including those of the olfactory and optic nerves
Sensory
_____ nerve – consists of motor fibers only
Many motor nerves are actually mixed nerves because they also carry sensory signals from muscles back to the CNS
motor
_______– a cluster of cell bodies outside the CNS (resembling a knot).
Ganglion
Proximal Branches (2)
Dorsal root- afferent signals
Ventral root- efferent signals
_____ _____ – innervates the muscles and joints in that region to the spine and the skin of the back
Dorsal ramus
______ ____ – innervates the ventral and lateral skin and muscles of the trunk and gives rise to the nerves of the limbs
In the thoracic region, it forms the intercostals nerve
Ventral ramus
Except in the thoracic region, the ventral rami form web-like nerve plexuses which carry signals from bones, joints, muscles, and the skin
Except in the thoracic region, the ventral rami form web-like nerve plexuses which carry signals from bones, joints, muscles, and the skin
o ______ Plexus (C1-C5) –
Great Auricular nerve (sensory nerve of skin of and around the ear)
Transverse Cervical nerve (sensory nerve of skin of ventral and lateral neck)
Ansa Cervicalis (motor nerve of omohyoid, sternohyoid, and sternothyroid)
Phrenic nerve (motor nerve of the diaphragm)
Cervical
_______ Plexus (C5-T1)
Axillary nerve
Radial nerve
Musculocutaneous nerve
Median nerve
Ulnar nerve
Brachial
________ Plexus (L1-L4)
Ilioinguinal nerve
Lateral femoral cutaneous nerve
Femoral nerve
Obturator nerve
Lumbar
______Plexus (L4-S4)
Superior gluteal nerve
Inferior gluteal nerve
Sciatic nerve
Tibial nerve
Common fibular (peroneal) nerve
Sacral
Each spinal nerve receives sensory input from a specific area of skin called a dermatome
Dermatomes overlap at their edges by as much as 50%, so severing one sensory nerve root does not entirely deaden sensation from a dermatome
Reflexes
Require stimulation – they are responses to sensory input
They are quick – they involve few if any interneurons and minimal synaptic delay
Involuntary – they occur without intent, often without our awareness, and they are difficult to suppress
Stereotyped – they occur in essentially the same way every time, in a predictable manner
Reflexes
Require stimulation – they are responses to sensory input
They are quick – they involve few if any interneurons and minimal synaptic delay
Involuntary – they occur without intent, often without our awareness, and they are difficult to suppress
Stereotyped – they occur in essentially the same way every time, in a predictable manner
_______ reflexes use simple neural pathways called reflex arcs that send signals from the sensory nerve ending to the spinal cord or brainstem and back to a skeletal muscle
Somatic
_______ reflex arc – simplest type of reflex arc, consisting only of a sensory neuron and a motor neuron (with just one synapse between neurons)
Monosynaptic
________reflex arc – reflex arc containing one or more association neurons
Polysynaptic
_________ reflex – CNS input and output are on the same side of the body
Ipsilateral
________ reflex – sensory input enters the spinal cord on one side of the body and the motor output leaves from the opposite side
Contralateral
__________reflex – Sensory signal enters the spinal cord at one level, and the motor output leaves the cord from a higher or lower level.
Intersegmental
