The Peripheral NS: Multiple Levels Of Organization

Question 1

CNS

Answer 1

Central nervous system, brain and spinal chord, brain can be divided into brain stem, with which cranial nerves other than CN1 are associated, cerebral hemispheres and cerebellum

Question 2

PNS

Answer 2

Peripheral nervous system, neurons or parts of neurons that exist outside CNS and connect CNS to other tissues of body. Includes Craninal nerves, spinal nerves, sympathetic trunk, ganglia and peripheral nerves

Question 3

Parts of neurons

Answer 3

Neural cell body, axon, dendrite

Question 4

Autonomic Nervous System

Answer 4

Visceral motor components PNS, controls smooth muscle, cardiac muscle, and glands. Has parasympathetic and sympathetic divisions

Question 5

Parasympathetic division ANS

Answer 5

Deals with vegetative functions and mechanisms that maintain tissue health and or build internal resources. Parasympathetic functions are typically active in animal at rest such as digestion, glycogen synthesis and storage in liver, slowing heart rate, reducing blood pressure, tearing, salivation, constricting pupils.
Parasympathetic pathways originate from brainstem and sacral spinal cord segments

Question 6

Sympathetic division of ANS

Answer 6

Prepares individual to deal with threatening/ stressful situations (fight of flight)
Increases heart rate, dilates pupils, relaxes airway smooth muscle -> dilation of airway, mobilizes glucose and fat energy stores.
Sympathetic pathways originate from thoracic and lumbar spinal cord segments
Works with PNS to maintain homeostasis

Question 7

Enteric Nervous system

Answer 7

Sensory, motor, and secretory neurons located in GI tract. Can function independently to control gut motility but receives input from sympathetic and parasympathetic system to help regulat gut function

Question 8

Nerve

Answer 8

Bundle of axons with surrounding connective tissue and blood vessels traveling the PNS. Nerve DOES NOT contain neuron cell bodies, nerve is NOT axon it is gross anatomical structure made of microscopic axons and connective tissue

Question 9

Nerve fiber

Answer 9

Can be used to refer to a single axon with in a gross nerve

Question 10

Ganglion

Answer 10

Cluster of neuron cell bodies in PNS

Question 11

Nucleus

Answer 11

Cluster of neuron cell bodies in CNS

Question 12

Afferent

Answer 12

Sensory pathway or neuron that carries info to CNS

Question 13

Efferent

Answer 13

Sensory pathway or neuron carrying info away from CNS (to control muscles and glands)

Question 14

Somatic

Answer 14

Refers to skeletal muscles, bones, joints, and skin

Question 15

Visceral

Answer 15

Refers to internal organs, blood vessels, glandular tissue

Question 16

Nervous system function

Answer 16

To provide communication between tissues and integrate and process info from environment and body. Recieves sensory (afferent) info from external and internal environment, processes info and generates appropriate motor response. Information picked up by sensory systems carried via nerves to CNS processed then motor command carried from CNS to effector tissue (muscles and glands) via nerves.

Question 17

CNS can influence

Answer 17

Movement, behavior, physiological processes by regulating levels of circulating hormones

Question 18

Functional tissues of nervous system

Answer 18

Neurons and glial cells
CNS- organized into grey and white matter
PSN- organized into ganglia and nerves
Grey matter and ganglia- contain neuron cell bodies and supporting glial cells
White matter and nerves- contain axons, supporting glial cells, and in nerve’s case connective tissue

Question 19

Neurons

Answer 19

Detect broad range of info about animals external and internal environment, integrate and process info via network of interconnected neurons and communicate with other body tissues to control movement and physiological function

Question 20

Sensory neurons

Answer 20

Detect mechanical, chemical, and thermal changes in tissues or receptor organs they innervation, information will then travel to CNS via nerves where it is processed by network interconnected neurons

Question 21

Motor neurons

Answer 21

Generate desired response via peripheral nerves and neurons releasing hormones into circulation based on information picked up by sensory neurons

Question 22

Parts of a neuron

Answer 22

Dendrites, axons, axon terminals

Question 23

Dendrites

Answer 23

Detect and recieve information from other neurons and gap junctions, specialized sensory receptors, chemical composition of extracelluar fluid, and via direct mechanical stimulation

Question 24

The Axon

Answer 24

Carries electrical signal called action potential over some distance, many are covered by myelin sheath to speed up conduction fo action potential. When nearing target tissue can split into branches or synapse with multiple target cells

Question 25

Axon terminals

Answer 25

At end of axon branches, may form close contacts with other cells, these contacts are called synapses Some axon terminals release neurotransmitters into circulation or into extracelluar space of tissues for more generalized effect

Question 26

Categories of neurons

Answer 26

Divided based on number of processes extending from cell body: Multipolar, pseudounipolar, bipolar Divided based on function: Sensory, motor, interneurons

Question 27

Chemical synapses

Answer 27

Occur at regions of close contact between axon terminal and another neuron or effector cell (muscle or gland), permits rapid communication between cells Action potential will reach synaptic terminal and synaptic vesicles within terminal will fuse with presynaptic membrane, neurotransmitter stored within synaptic vesicles released into synaptic cleft where it can bind to receptors on post synaptic membrane. These receptors will bind directly or indirectlyy to influence the flow of ions through post synaptic membrane. This binding leads to alteration of membrane potential of post synaptic cell leading to synaptic potential and potentially leading to action potential, muscle contraction, cellular secretion etc.

Question 28

Sensory Neurons

Answer 28

Also known as afferent neurons. Detect and/or convey mechanical, chemical, and thermal changes in tissue or receptor organs they innervation. Types include somatic and visceral afferent neurons and special sensory afferent neurons (vision, hearing, vestibular, taste and smell)

Question 29

Afferent neurons

Answer 29

Psuedounipolar neurons that carry sensory info from visceral or somatic tissues to CNS. Dendrites- located in peripheral tissues and viscera Axon- Peripheral process of neuron travels from innervated tissue to dorsal root or cranial ganglion via peripheral nerves, The peripheral process functions as axon Cell Body- located in dorsal root ganglion or cranial nerve ganglion, peripheral location allows action potential to travel along axon without having to pass through cell body Central process- also functions as axon, enters CNS and synapses on neurons involved in processing sensory information

Question 30

Nociceptors

Answer 30

Neurons that convey sensory information regarding tissue damage or potential for damage Can be experienced as pain or trigger reflex of withdrawal Dendrites- exist as free nerve endings in tissues such as skin and viscera and are stimulated by intense deformation or damage, and by chemical mediation’s released by damaged cells

Question 31

Mechanoreceptors

Answer 31

Detect tactile pressure and vibration type stimuli; ex Pacinian corpuscles found in skin and viscera, specialized connective tissue encapsulation of neruron endings allows neurons to detect subtitle differences in quality of different timelines Baroreceptors- in aortic arch and other blood vessels detect stretch in vessel wall which is related to blood pressure

Question 32

Proprioreceptors

Answer 32

Detect stimuli related to body movement or position Ex muscle spindles, convey info about muscle fiber length via intrafusal muscle fiber that has free nerve ending spiraled around it when muscle is stretched it deforms the spiral which opens ion channels -> membrane potential

Question 33

Special sensory afferent neurons

Answer 33

Most are bipolar Dendrites may be associated with specialized receptor cells (auditory and vestibular system) Afferent neuron itself may function as the receptor (Olfactory system) Cell body- may be in a ganglion or within receptor tissue Axons- join or corm cranial nerves to travel to brain

Question 34

Interneurons

Answer 34

Reside in CNS, some are located peripherally in ganglia and in viscera, connect afferent (sensory) and efferent (motor) neurons Multipolar (recieve and integrate inputs from up to a thousand neurons and convey output to other neurons); can have excitatory or inhibitory effect on other neurons Axons- may synapse on near by neurons or project long distances between regions of CNS

Question 35

Motor neurons

Answer 35

Aka efferent neurons, project to peripheral tissues and produce response in those tissues Include somatic and visceral efferent neurons Neurosecretory neurons- provide another form of output from CNS

Question 36

Somatic Motor Neurons

Answer 36

Large, multipolar neurons, “Lower motor neurons” (neurons in CNS are upper motor neurons) UMNs carry motor commands from brain to LMN in spinal chord or brainstem, UMN do not leave CNS or shynapse directly onto muscle Heavily myelinated and big to maximize speed of transmission Cell body and dendrites- located in CNS in ventral horn of spinal chord or in cranial nerve nuclei in brain stem, recieve input from UMN for voluntary movement and other movement requiring control from brain, and somatic afferents and local reflex circuits Axon- leave CNS via ventral root or a cranial nerve and projects via spinal nerves and more peripheral nerves or via cranial nerves to innervation skeletal muscle

Question 37

Neuromuscular junction

Answer 37

Synapse formed with skeletal muscle fiber

Question 38

Somatic Motor Neuron cell body and axon location

Answer 38

Cell body and dendrites are located in CNS in the ventral horn of spinal chord or in cranial nerve nuclei of brain stem Axon- leaves CNS via ventral root or cranial nerve and projects via spinal nerves and more peripheral nerves or via cranial nerves to innervation skeletal muscle

Question 39

Visceral motor neurons

Answer 39

Multipolar 1st cell body (and dendrites) located in CNS Sympathetic NS- preganglionic neuron cell body located in lateral horn thoracolumbar spinal chord (T1-L4) Parasympathetic NS- preganglionic cell body located in brain stem or sacral spinal chord (S1-S3) Synapse on neuron 2 in peripheral ganglion can be focused and specific or can be neurotransmitter release to neutropil to affect neurons diffuse lay 2nd cell body (and dendrites)- located in peripheral ganglion Multipolar neurons Autonomic synapse- may be no defined synapses are target smooth muscles so neurotransmitter is released and diffuses and acts on smooth muscle in vicinity this leads to slower neurotransmitter effect on ANS; autonomic efferent neurons can form synapse with cells of glands

Question 40

Neurosecretory neurons

Answer 40

Contribute to output of nervous system Axon projects to capillary beds where substances can be released from axon terminals and enter blood stream to affect distant organs

Question 41

Spinal chord neural organization

Answer 41

Grey matter: contains neuron cell bodies, shaped like H - Dorsal Horn- contains neurons involved in sensory processing - Ventral Horn- Contains motor neurons involved in somatic motor system which controls skeletal muscle - Intermediate grey- grey matter between dorsal and ventral horn - Lateral horn- part of intermediate grey, contains motor neurons of sympathetic division of ANS, only present in spinal chord segments T1-L4

Question 42

White Matter

Answer 42

Surrounds grey matter in spinal chord, contains axons traveling into and out of spinal cord and cranially and caudally with in spinal cord

Question 43

Spinal cord segments

Answer 43

36 in dogs and cats, every segment gives rise to pair of spinal nerves C8T13S3Cd5

Question 44

Spinal nerves

Answer 44

Attach to spinal cord via dorsal and ventral roots Dorsal roots- contain sensory axons traveling to spinal cord, cell bodies for these axons in dorsal root ganglia Ventral roots- contain motor axons leaving spinal cord, cell bodies are located in ventral and lateral horn of spinal cord Spinal nerves exit vertebral canal via intervertebral foramina

Question 45

Intervertebral foramina

Answer 45

Spinal nerves exit vertebral canal via intervertebral foramina between successive vertebrea 3 main branches- dorsal branch, ventral branch, communicating branch

Question 46

Dorsal branch

Answer 46

One of 3 branches of intervertebral foramina; supplies motor and sensory innervation to epaxial muscles and dorsal body wall

Question 47

Ventral branch

Answer 47

One of 3 branches of intervertebral foramina Supplies motor and sensory innervation to hypaxial muscles and lateral and ventral body wall

Question 48

Communicating branch

Answer 48

AKA ramus communicans this is one of 3 branches of intervertebral foramina, connects spinal nerve to sympathetic trunk (or vertebral nerve in neck)

Question 49

Spinal nerve roots vs branches

Answer 49

Roots connect spinal nerves to spinal cord via dorsal and ventral roots (dorsal sensory, ventral motor), branches are where spinal nerves exit the vertebral canal via intervertebral foramina between successive vertebrea (dorsal branch, ventral branch, communicating branch) (dorsal epaxial muscles and dorsal body wall, ventral hypaxial muscles and ventral and lateral body wall, communicating spinal nerve connection to sympathetic trunk or vertebral nerve in neck)

Question 50

Innervation patterns for limbs and viscera

Answer 50

Segmental organization is less apparent than in these innervation patterns. Brachial and lumbosacral plexuses consist of intermingling axons from multiple spinal nerves

Question 51

Vertebral column

Answer 51

Bony structure made up of articulated vertebrae

Question 52

Vertebrae structure

Answer 52

Have a body and an arch, arch is composed of 2 Pericles and 2 laminae which fuse dorsally; body and arch enclose to form vertebral foramen (opening)

Question 53

Vertebral canal

Answer 53

This is where spinal cord resides, formed by sum of vertebral foramina in an articulated vertebral column. On other side intervertebral foramen permits passage of spinal nerve and segmental spinal artery and vein

Question 54

Vertebrae categories

Answer 54

C- cervical T- Thoracic L- Lumbar S- Sacral Cd- Caudal Vertebral formula (dog/cat)- C7T13L7S3Cd~20 Spinal cord segments (dog/cat)- C8T13L7S3Cd5

Question 55

Intervertebral foramina

Answer 55

Spinal nerves exit vertebral canal via these; 8 cervicle spinal cord segments but only 7 cervical vertebrea therefore Spinal nerve C1 enters via a foramen in cranial part of atlas, Spinal nerves C2-C7 exit via IVF cranial to the nominally corresponding vertebrea (ie spinal nerve C2 exits crainial to vetebra C2) Spinal nerve C8 exits via IVF crainial to vertebra T1 Spinal nerves T1-Cd5 exit IVF caudal to nominally corresponding vertebrea (spinal nerve T12 exits via IVF caudal to vertebra T12)

Question 56

Sympathetic trunk

Answer 56

Runs longitudinally along ventrolateral aspect of vertebral bodies, consists of axons and segmental ganglia associated with each spinal nerve from T1->Caudal spinal nerves (ie to the tail) Crainially continues as sympathetic trunk component of vagosympathetic trunk Sympathetic trunk is bilateral

Question 57

Ansa subclavia

Answer 57

Near thoracic inlet axons within sympathetic trunk divide to form loop around subclavian artery called ansa subclavia

Question 58

Motor neurons in visceral tissues name

Answer 58

Called visceral efferent

Question 59

Visceral efferent pathways

Answer 59

Consists of a series of 2 VE neurons Neuron 1- Preganglionic neuron has cell body in CNS Neuron 2- Postganglionic neuron has cell body in autonomic ganglia in PNS

Question 60

Sympathetic pathway generalizations

Answer 60

Sympathetic division ANS originates from VE neurons, cell bodies in lateral horn spinal cord grey matter in T1-L4 spinal cord (guesstimate which segment neuron is located in based on position in body) Axons of neuron 1 exit spinal cord via ventral root and travel to spinal nerve into communicating branch to sympathetic trunk. Axon of neuron 1 then follows nerve roads to neuron 2 (sympathetic trunk and ganglia, vertebral nerve, abdominal sympathetic ganglia, splanchic nerves, hypogastric nerves, pelvic ganglia) Cell body of neuron 2 (postganglionic neuron) will usually be located in the sympathetic ganglion closest to target organ (ie sympathetic trunk ganglia, abdominal sympathetic ganglion, pelvic ganglion); axon of neuron 2 reaches target organ by following nerves and blood vessels to organ or coursing directly to target organ

Question 61

Cardiac nerves

Answer 61

Axons forge their own path from middle cervicle ganglion to heart as cardiac nerves