BIO 167 Exam 6 Learning Targets

Describe the gross anatomy of the spinal cord

• 31 segments

  • each giving rise to a pair of spinal nerves

• protected by bone, meninges, and CSF

Describe the location of the spinal cord

• located w/in the vertebral canal

• foramen magnum → 1st/2nd lumbar vertebra

Explain how specific spinal nerves pass enter/exit the vertebral canal

cervical enlargement

where nerves serving upper extremities arise

lumbar enlargement

where nerves serving lower extremities arise

conus medullaris

tapered end of the spinal cord

filum terminate

• pia mater extension to coccyx

• holds spinal cord in position

• contains no neurons, only connective tissue

cauda equina

lower spinal nerve roots that “chase” their exits

spinal segment

spinal nerve

Describe the structure, location and extent of the spinal meninges.

• composed of dura mater, arachnoid mater, and pia mater

• foramen magnum to the coccyx, separating the spinal cord from the vertebral canal

List in order the structures passed from the bone of the vertebra to the surface of the spinal cord.

1. epidural space

2. dura mater

3. subdural space

4. arachnoid mater

5. subarachnoid space

6. pia mater

   1. denticulate ligament

7. lumbar cistern

epidural space

contains fat

subdural space

deep to dura mater

subarachnoid space

• contains CSF

• deep to arachnoid mater

denticulate ligament

extensions connecting spinal cord to dura mater meninx

lumbar cistern

space for lumbar puncture

subdural space functional significance

• potential space acts as a structural buffer

• allows for minor movement between meningeal layers

• houses "bridging veins" that drain blood to venous sinuses

• acts as part of the lymphatic system around the spinal cord

subarachnoid space functional significance

• protecting and nourishing CNS

• cushions spinal cord

denticulate ligament functional significance

• stabilize the spinal cord within the dura mater, suspending it within the cerebrospinal fluid

• anchors spinal cord laterally to prevent excessive side-to-side motion

lumbar cistern functional significance

• safe, accessible reservoir of CSF for lumbar puncture

anterior median fissure

deeper groove running length of spinal cord

posterior median sulcus

shallower groove

gray commissure

• bridge connecting masses of gray matter

• encloses central canal

central canal

• continuous w/in chamber in brain

• contains CSF

• runs length of spinal cord

ventral horns

• have some interneurons

• mainly house cell bodies of somatic motor neurons

  • axons exit cord via ventral rootlets, which fuse into ventral roots of spinal cord

  • amt of ventral gray matter = amt of skeletal muscle innervation at that level = spinal cord enlargements

dorsal horns

consist of interneurons

lateral horns

• thoracis and superior lumbar segments

• mainly consist of cell bodies of autonomic motor neurons to visceral effectors (sympathetic division)

  • neurons exit cord through ventral root

anterior columns

• ventral

• composed of myelinated and nonmyelinated fibers

posterior columns

• dorsal

• composed of myelinated and nonmyelinated fibers

lateral columns

• lateral

• composed of myelinated and nonmyelinated fibers

functional neuron associated w/ anterior horn

• cell bodies of somatic motor neurons

  • some interneurons

functional neuron associated w/ lateral horn

cell bodies of autonomic motor neurons

functional neuron associated w/ posterior horn

interneurons

general fxn of the spinal cord

• provides 2-way conduction pathway to and from brain

• major reflex center

list the number and name of spinal nerves

1. cervical spinal nerves: C1 - C8

2. thoracic spinal nerves: T1 - T12

3. lumbar spinal nerves: L1 - L5

4. sacral spinal nerves: S1 - S5

5. coccygeal nerves: Co1

describe if the nerves are mixed, sensory, or motor

describe the length of a spinal nerve

name the types of fibers that travel through the dorsal root and ventral root

• dorsal root: carries sensory info

• ventral root: carries motor info

name the branches of a typical spinal nerve and describe the regions or structures innervated by these branches

spinal nerve plexus

name the 4 plexuses of the body

1. cervical plexus

2. brachial plexus

3. lumbar plexus

4. sacral plexus

cervical plexus location

deep to sternocleidomastoid

brachial plexus location

located in neck and axilla

lumbar plexus location

w/in psoas major

sacral plexus location

along the posterolateral wall of pelvis

ventral rami of cervical plexus

C1 - C4 (C5)

ventral rami of brachial plexus

C5 - T1

• often receiving fibers from C4 and T2

ventral rami of lumbar plexus

L1 - L4

ventral rami of sacral plexus

L4 - S4

• “lumbosacral trunk” = L4 + L5 contributions

cutaneous branches of cervical plexus

skin over back of head, ear region, anterior neck, and shoulder region

cutaneous branches of brachial plexus

skin over shoulder and all parts of upper extremity

cutaneous branches of lumbar plexus

skin over lower abdomen, buttock, external genitalia, many thigh regions, medial leg and foot

cutaneous branches of sacral plexus

skin over gluteal region, external genitalia, and lower extremity

innervations of intercostal nerves

cervical plexus motor branch

• muscles on back of neck: trapezius, sternocleidomastoid

• diaphragm: phrenic nerve - fibers from C3 - C5

brachial plexus motor branch

muscles of shoulder and upper extremity

lumbar plexus motor branch

muscles of lower abdomen, medial and anterior thigh regions

sacral plexus motor branch

muscles of lower extremity

what is a dermatome and its clinical significance

area of skin supplied by cutaneous branches of a single spinal nerve

• damage to the spinal cord can be determine by which dermatomes are affected (skin poke)

reflex

rapid, automatic response to stimuli

reflex arc

conduction pathway involving two or more neurons

reflex center

identify and describe the components of a simple reflex arc

1. receptor

2. sensory neuron

3. integration center

4. motor neuron

5. effector

Rod Stewart Is My Everything

give an example of how a reflex helps to maintain homeostasis

visceral reflexes help maintain heart rate, respiration, digestion, and urination

functional classification of reflexes

• somatic

• visceral

intrinsic reflex

born with

• unlearned, unpremeditated, involuntary

• ex: help maintain posture, avoid pain and injury, control visceral activities

acquired reflex

results from practice and repetition

• ex: driving skills, playing a musical instrument

somatic reflex

activate skeletal muscles

• maintain homeostasis w/ skeletal muscle contractions

visceral reflex

activate visceral effectors

• cardiac and smooth muscles

• glandular secretion

• help maintain homeostasis associated w/ heart rate, respiration, digestion, and urination

types of spinal reflexes

somatic reflexes mediated by the spinal cord

• stretch reflex

• tendon reflex

• flexor (withdrawal) reflex

• crossed-extensor reflex

stretch reflex

muscle tightens in response (patellar reflex)

• antagonist relaxes

tendon reflex

muscle relaxes in response

flexor (withdrawal) reflex

finger pricked w/ needle

crossed-extensor reflex

ipsilateral withdrawal reflex and contralateral extensor reflex

describe the ANS

system of motor neurons innervating smooth and cardiac muscle, and glands

name some visceral functions controlled by the ANS

• speeds or slows heart rate

• shunts blood to areas in need

• adjust blood pressure and body temperature

• increases or decreases stomach secretions

give examples of visceral effectors

smooth and cardiac muscle, glands

2 principle divisions of the ANS

• parasympathetic

• sympathetic

parasympathetic division

rest and digest

• promotes maintenance functions and conserves body energy

sympathetic division

fight/flight system

• mobilizes body during activity or threatening situations

describe the general effects of each division

parasympathetic effects

• energy use by body is low

• directs activities like digestion, pooping, and peeing

• ex: after eating

  • blood pressure drops

  • heart rate drops

  • eyes accommodate for close reading

  • GI tract is actively digesting food

sympathetic effects

• exercise, embarrassment, excitement, emergency

• increase in heart rate, respirations

• dry mouth, cold and sweaty skin, dilated pupils

• visceral blood vessels constrict

• bronchioles in lungs dilate

• liver releases more glucose into blood (more energy)

• nonessential actions (digestion) are slowed

describe the “two-neuron hook-up” of the ANS

preganglionic neuron - autonomic ganglia - postganglionic neuron

• uses chain to reach effector

describe the origin and termination point of a preganglionic and postganglionic neuron in the parasympathetic and sympathetic nervous system

give the general name of the “autonomic ganglion” of the parasympathetic nerveous system and describe its location

terminal ganglia

• near or w/in walls of visceral effector organ

give the general names of the “autonomic ganglia” of the sympathetic nerveous system and describe their locations

1. sympathetic chain ganglia: paravertebral ganglia

2. collateral ganglia: close to large abdominal arteries

lie close to the spinal cord

describe the general trends with respect to the location of ganglia and the length of the postganglionic fiber in the parasympathetic and sympathetic systems

describe the specific organization of the sympathetic division of the ANS

identify the origin of the preganglionic sympathetic fibers and describe the path taken by these fibers to enter the sympathetic trunk

describe the 3 possible routes taken by the preganglionic fibers once in the sympathetic trunk

describe the three possible routes taken by the preganglionic ribers once in the sympathetic trunk

describe how the sympathetic fiber leaves the sympathetic trunk to rejoin the spinal nerve

describe the origin and termination point of the postganglionic sympathetic fiber

describe the sympathetic trunk

explain the relationship b/t chromaffin cells in the adrenal medulla and the sympathetic division

white ramus communicans

splanchnic nerve

gray ramus communicans