1/10 Britton Autonomic and Nerve Physiology Flashcards
CNS
Brain and spinal cord
PNS
Nerves that branch out from CNS al over the body
Functional divisions of the nervous system
- Afferent
- Efferent
_____ detects stimuli from the periphery and conduct APs to the CNS and are termed _____
Afferent; sensory neurons
____ conducts APs from the CNS to effector organs, which are called _____
Efferent; motor neurons
The ANS is responsible for the:
Unconscious activities of the body (ex. heart rate, blood pressure, GI tract motility, pupil dilation, saliva stimulation)
Divisions of the ANS
- Sympathetic (fight or flight, mobilize body’s resources)
- Parasympathetic
Many organs have ____ innervation
Dual
Generally, SNS and PSNS have opposing ____ effects on target organs. The actions of the 2 divisions must be balanced in order to maintain _____
Antagonistic; homeostasis
Arrangement of neurons in the ANS: both divisions of the ANS contain ____ and _____
Pre-ganglionic and post-ganglionic neurons
Preganglionic neurons have cell bodies located within the
CNS
Pre-ganglionic neurons of the SNS are located:
Within the spinal cord segments T1-L3
SNS and PSNS have complementary effect in:
- Increasing salivary secretion
- sympathetic increases thickness and viscous
- PSNS increases watery secretion
In the SNS, the preganglionic neuron is _____ than the post-ganglionic neuron
Shorter
In the PSNS the preganglionic neuron is _____ than the post-ganglionic neuron
Longer
Pre-ganglionic neurons of the PNS are located:
In the craniosacral regions of the CNS
Pre-ganglionic neurons release NT’s onto:
Post-ganglionic neurons
In the SNS, the pre-and post-ganglionic neurons synapse:
In the paravertebral ganglia
In the PNS, the pre-and post-ganglionic neurons synapse:
Near or in the effector organs
True or false: Adrenal medulla is stimulated both by the SNS and PSNS
False- only SNS
After synapsing, post-ganglionic neurons then release NTs onto:
Effector organs
Do parasympathetic nerves innervate the blood vessels?
No, only SNS
Postganglionic neurons of the ANS store neurotransmitter within vesicles in ____ and release neurotransmitter over the surface of the target tissue
axon varicosities
Autonomic nerves are divided into what 2 groups?
- Cholinergic
- Adrenergic
Transmission of nerve impulses mediated by Ach
Cholinergic
Transmission of nerve impulses mediated by NE and E
Adrenergic
Noradrenaline is an alternative name for:
Norepinephrine (hence adrenergic)
Cholinergic nerves can synapse with what types of receptors?
- Nicotinic (ligand-gated)
- Muscarinic (GPCR)
Adrenergic nerves can synapse with what types of receptors?
- alpha-1
- alpha-2
- beta-1
- beta-2
- beta-3
(all adrenergic receptors which are GPCRs)
Cholinergic receptors bind:
Ach
Where are nicotinic receptors located?
- all post-ganglionic neurons of the ANS
- adrenal medulla
- neuromuscular junction of somatic nerves
Nicotinic receptors are _____
Ligand gated ion channels
True or false: nicotinic receptors are inhibitory usually
False - usually excitatory
Muscarinic receptors are ____
G-protein coupled receptors
Location of muscarinic receptors
- All effector glands and tissue innervated by the PNS (M1, M2, M3)
- Sweat glands innervated by the SNS
Muscarinic receptors can be ____ or _____
Excitatory or inhibitory
Why are muscarinic receptors both excitatory and inhibitory?
Depends on the associated G-protein and downstream signaling pathway
Examples of parasymapthetic nervous system effectors
- smooth muscle
- gland cells
- nerve terminals
- cardiac muscle
Examples of sympathetic nervous system effectors
- sweat glands
- smooth muscle
- gland cells
- nerve terminals
- cardiac muscle
- renal vasculature
- smooth muscle
- cardiac muscle
- vessels
Somatic nerves synapse at _____. The NT associated is always ____
Skeletal muscle; Acetylcholine
Almost all _____ are adrenergic neurons, meaning that they release ____. All adrenergic receptors are ____
Sympathetic post-ganglionic neurons; GPCR’s
Activation of adrenergic receptors on effector glands and tissues initiates:
Diverse G-protein intracellular signaling mechanisms
Key locations of adrenergic receptors (alpha-1)
- blood vessels
- eye
- bladder
- prostate
Key locations of adrenergic receptors (alpha-2)
- blood vessels
- GI tract smooth muscles
- CNS
Key locations of adrenergic receptors (beta-1)
- heart
- kidney
- GI tract smooth muscle
Key locations of adrenergic receptors (beta-2)
- lung
- liver
- blood vessels
Key locations of adrenergic receptors (beta-3)
detrusor muscle of the bladder
Subunits of G proteins
alpha, beta, gamma
True or false: G proteins can have a different set of alpha, beta, gamma subunits
True
Regarding G proteins, there are many different ___ subunits
alpha
The G protein complex is often characterized by:
The type of alpha subunit present
Examples of G protein alpha subunits: Ga(s)
Stimulated adenylyl cyclase
Examples of G protein alpha subunits: Ga(i)
Inhibits adenylyl cyclase
Examples of G protein alpha subunits: Ga(q)
Activated PLC-beta
True or false: GPCRs are dimeric
False - heterotrimeric
Somatic nervous system subdivision of the peripheral nervous system has 2 main functions, which are:
- sensory input
- movement control
Motor functions of the somatic nervous system are responsible for:
- maintaining the body’s posture and balance
- moving the trunk, head, links, tongue, eyes
- communicating through facial expressions and speech
The somatic nervous system is a _____ - under conscious control
Voluntary motor system
What are voluntary movements?
Movements that are consciously activated to achieve a specific goal, such as walking, typing chewing
True or false: Although consciously activated, the details of most voluntary movements occur automatically
True
Reflexes are ____ movements
Involuntary (occur without conscious thought)
Reflexes are mediated through ____ and are responsible for ____ body movements
spinal cord and brainstem; some
What is motor control?
Senses –> cognition –> action
Through our ____, we perceive the world and our relationship to it
Senses
What is cognition?
CNS processes sensory input to construct details of the environment
Conscious actions require ________ to make actions adaptive and appropriate for a particular situation
Sensory input and cognitive processing
In motor control, the final output is:
A set of commands to certain muscles in the body (ex. run from predator, seek shelter from rain, search for food when hungry, move lips and vocal cords to communicate)
At the highest level, ____ controls voluntary movements
Motor cortex
Motor cortex function
Processes information related to the planning and coordination of whole-body movements
_____ make essential contributions to motor control
Basal ganglia and cerebellum
At the most basic level, movement is controlled by _____, often with no help from the ____
Spinal cord; brain
True or false: Distinct but highly interactive regions make similar contributions to motor control
False - UNIQUE contributions
Voluntary movements result from stimulation of ____ neurons
Upper and lower motor neurons
Upper motor neurons:
Cell bodies are in the _____
Axons form ____ that connect to _____
- Cerebral cortex
- Descending tracts; lower motor neurons
Lower motor neurons: cell bodies are in:
- Cranial nerve nuclei
- Anterior horn of spinal cord
Where do lower motor neurons send their axons out? What do they innervate?
Out of the brainstem and spinal cord; innervate skeletal muscles of the head and body (respectively)
All commands for movement, whether voluntary or reflexive, are ultimately conveyed to ____ by activity of ____
Skeletal muscles; Lower motor neurons
Somatic motor neurons are also called:
Alpha motor neurons
Motor neurons that control limb and body movements are located in the ____ of the ___
Anterior horns of the spinal cord
Somatic motor neurons synapse directly with:
Skeletal muscle and the NMJ
What is a motor unit?
1 motor neuron plus all the muscle fibers that it innervates
A single motor neuron can branch at its axon terminal and innervate multiple fibers
Motor units allow for:
Coordinated response of larger muscles
A single muscle muscle fiber receives how many synapses? What does this mean?
One; Muscle cell is dependent on a single motor neuron for activation, providing great specificity for muscle control
Motor unit pool
All the motor units within a muscle
Motor units vary greatly in ____; a single somatic motor neuron may innervate ____ muscle fibers
Size; 3 to 2,000
What is a small motor unit?
A single motor unit which innervated only a few muscle fibers
Small motor units allow for:
Fine motor control in that muscle (ex. muscle that controls eye movement, fingers)
What is a large motor unit?
A single motor unit which innervates thousands of muscle fibers
Function of large motor unit
Coordinate the response of large muscles (ex. control large limb muscles, posture, walking)
Different types of movements result from:
The activation of small and large motor units
Motor unit recruitment: Increasing the number of motor units active at any one time increases ____
The amount of force produced by a muscle
The progressive activation of motor units is called:
Recruitment
The contraction of a whole muscle often require:
Hundreds of motor neurons to fire APs
In what order are motor units recruited?
In a fixed order, according to their size
True or false: Larger motor units are recruited and fire APs before smaller motor units are recruited
False: smaller before larger
During motor unit recruitment, when synaptic input increases, what happens?
- Progressively larger motor units are recruited
- results in gradual increase in muscle contraction
The orderly recruitment of motor neurons by size is known as:
Motor unit size principle
Motor unit recruitment ____ the strength of muscle contraction
Increases
AP frequency of motor neurons: frequency refers to ____
The number of APs delivered to a muscle within a set period of time
An increase in the frequency of APs generated by motor neurons will:
Increase muscle contraction
The increase in muscle force that occurs with increased AP frequency reflects the ____ of successive muscle contractions
Summation
The muscle fibers are activated by the next AP before _____, and the forces generated by the temporally overlapping contractions are ____
They have had time to completely relax; Summed
At the highest AP firing rated, summation grows stronger and individual muscle fibers become in a state of _____
Tetanus
What is tetanus?
- state of sustained maximal muscle contraction
- also infectious disease caused by tetanospasmin
True or false: muscle has time to relax between successive stimuli during tetanus
False
Tetanus infection generally occurs through:
Wound contamination and often involves a cut or deep puncture wound
____ is the site of many interneurons and complex neural circuits that perform the nuts and bolts of processing motor control
Spinal cord
Spinal cord neurons can take charge of ____
Reflex movements
What is a reflex?
Involuntary reaction in response to a stimulus applied to the periphery and transmitted to the CNS
_____ allow quicker reaction to stimuli than is possible by conscious thought
Reflexes
3 classes of nerves are the basic constituents of all neural circuits
- sensory (afferent neurons)
- interneurons
- motor (efferent neurons)
Components of a reflex arc are labeled in the order in which ____
AP;s pass through them
Components of a reflex arc
- receptor
- sensory neuron
- interneuron
- motor neuron
- effector organ
In a reflex arc, ___ synapses with the interneuron at the _____
Afferent nerve; dorsal root
Proper control of muscle function requires:
- excitation of the muscle by the spinal cord anterior motor neurons
- continuous feedback of sensory information from each muscle to the spinal cord
Proprioception
Sense of the body’s position in space based on specialized receptors that reside in the muscles and tendons
Types of muscle receptors
- Muscle spindle
- Golgi tendon organ
____ signals the changes in the length of a muscle
Muscle spindle receptor
____ signals the amount of force being applied to a muscle
Golgi organ tendon receptor
Muscle spindles are ____ that are located within _____
Sensory receptors; the muscle itself
Function of muscle spindles is to:
Detect changes in muscle length and the speed of change in muscle length
Muscle spindles are referred to as ____
Intrafusal fibers
Each muscle contains ___ muscle spindles
Many
True or false: muscles necessary for fine movements contain less spindles than muscles that are used for posture or coarse movements
False - contain MORE
When muscles lengthen, what happens to muscle spindles?
They stretch
Muscle spindle stretch causes ____. This results in ____
AP’s to sent to the spinal cord; STRETCH REFLEX –> activation of more motor neurons at the spinal level that send an impulse back to the muscle, signals the muscle to contract with greater force to decrease the speed at which the muscle is being stretched
Examples of stretch reflex
- maintain proper posture
- knee jerk test
- protection from potential damage
Where is golgi tendon organ located?
Between muscle and tendon
Golgi tendon organ (GTO) signals information about:
The load or force being applied to the muscle
When a GTO is stimulated, it causes:
Associated muscle to relax by interrupting its contraction (autogenic inhibition)
The function of the GTO can be considered ____ of the muscle spindle
Opposite (serves to produce muscle contraction)
Swallowing reflex: can be initiated ____ but thereafter it is almost entirely under ____
Voluntarily; reflex control
Phases of swallowing
- oral phase
- pharyngeal phase
- esophageal phase
Oral phase of swallowing occurs ____ when the bolus of food is passed down towards the pharynx by ____
Voluntarily; elevating the tongue (a conscious decision)
During the oral phase of swallowing, what nerves are activated?
- sensory nerves from CN 5 and 9 in the pharynx
- integration in the medulla initiated involuntary swallowing reflex
Pharyngeal phase of swallowing occurs ____ when food enters the pharynx
Involuntarily
Esophageal phase of swallowing occurs ____ in the esophagus
Involuntarily
Steps of pharyngeal phase swallowing
- activation of somatic and vagal nerved innervating skeletal muscle of pharynx; closes trachea
- inhibition of vagal nerves at upper esophageal sphincter causes relaxation of UES
- activation of vagal nerves innervating skeletal muscle of esophagus, causing a primary peristaltic contraction
Steps of esophageal phase of swallowing
- activation of vagal nerves innervating smooth muscle of the esophagus
- activation of enteric nerves leads to continued peristaltic waves along esophagus
- relation of the lower esophageal sphincter and receptive relaxation of the stomach
What does the gag reflex involve?
Brisk and brief elevation of the soft palate and contraction of the pharyngeal muscles
Gag reflex is stimulated by:
Touching posterior pharyngeal wall
Gag reflex: sensory limb mediated by ____; motor limb by ____
CN 9; CN 10
Touching the soft palate can lead to ___
Similar reflex response as the gag reflex - sensory limb is CN V
True or false: gag reflex rarely interferes with dental procedures
False - often