BSU a&p exam 5

5 anatomic divisions of the spinal cord

cervical, thoracic, lumbar, sacral, and coccygeal,

How many pairs of spinal nerves are there?

31

why are spinal nerves considered mixed nerves?

they contain both motor and sensory fibers, allowing them to transmit signals in both directions between the spinal cord and the body.

From outermost to inner most what are the 7 structures and spaces that encircle the spinal cord

the vertebrae, epidural space, dura mater, arachnoid mater, subarachnoid space, pia mater.

which space is csf collected from in a lumbar puncture

the subarachnoid space

What type of neurons are found in the anterior horns?

primarily motor neurons t

what nuclei is found in the anterior horns?

lower motor neuron nuclei,

what neurons are found in lateral horns?

autonomic motor neurons

what nuclei is found in lateral horns?

what neurons are found in posterior horns

sensory neurons and interneurons

what nuclei is found in posterior horns?

Posterior horn nuclei process sensory information from the body and are involved in reflex actions.

what neurons are found in the gray commisure?

Interneurons and commissural neurons

what nuceli is found in the gray commisure?

interneuron nuclei

do funniculi contain motor or sensory axons or both?

Both

Conduction pathways consist of____ and a ____

ascending tract; descending tract

What is a tract?

A tract is a bundle of axons in the central nervous system that share a common function, either carrying information to or from specific areas of the brain or spinal cord.

What is a nucleus in spinalc cord?

A nucleus in the spinal cord is a cluster of neuronal cell bodies located within the central nervous system that typically shares a common function and connects with specific nerve pathways.

Sensory pathways

• ascending pathways; from sensory receptors ascending to brain

motor pathways

• Descending pathways; from brain to mucles and/or glands

Decussate

• most; point can vary slightly from pathway to pathwaywhere nerve fibers cross from one side of the central nervous system to the other, typically at the junction of the brainstem and spinal cord or at other specific points along the pathway.

Contralateral

• referring to the side of the body opposite to that of a given structure or activity, often used in the context of pathways that affect the opposite side of the body. can merge

ipsilateral

• referring to the same side of the body as a given structure or activity, often used in contrast to contralateral.

Primary neuron of sensory pathway

dendrites part of receptor that detects stimulus, cell bodies in posterior root ganglia; axons to secondary neuron in CNS

secondary neuron of sensory pathway

• Interneuron; within posterior horn of cord or brainstem nucleus

• projects to thalamus or cerebellum 

Teritiary neuron of sensory pathway

• nterneuron residing in thalamus; axon to primary somatosensory cortex

Actions of motor pathways

travel to hubs before getting where needed

motor pathways

• Descending pathways in brain & spinal cord

• Control skeletal muscle

upper motor neuron

• Excites or inhibits lower motor

• cerebral cortex or brain stem

lower motor neruon

anterior horn or brainstem

excitatory only

secretes ach to muscle

involuntary movement

direct path ways

• responsible for conscious control of skeletal activity

• Primary motor cortex => axons into brainstem or spinal cord

• 1 lower motor neuron

indirect pathways

• responsible for subconscious or unconscious control

• ANS

• 2 lower motor neurons

somatic nervous system

voluntary movement

somatic sensory portion

• detects stimuli from special senses, skin, and proprioceptors => sends info to CNS

somatic motor portion

• transmits nerve signals from CNS to control skeletal muscles

autonomic nervous system

unconscious movement

visceral sensory

detects stimuli from blood vessels and internal organs

autonomic motor

• transmits nerve signals to cardiac muscle, smooth muscle, and glands

charachteristics of SNS motor neurons

• extends from CNS to skeletal muscle fibers

• cell body within brainstem or spinal cord => exits CNS in cranial or spinal nerve

• myelinated axons with large diameter

  • fastest conduction

• always release acetylcholine (ACh) from synaptic knob

Chachteristics of ANS motor neurons

• Myelinated axons with small diameter

  • slower conduction

• releases ACh from synaptic knob

preganglionic neuorn

A neuron that transmits signals from the central nervous system to a ganglion in the autonomic nervous system.

preganglion axon

ganglionic neuron

A neuron that transmits signals from a ganglion to target organs in the autonomic nervous system.

postganglionic neuron

• cell body in autonomic ganglion => exits to effector (muscle or gland)

neuronal convergence

• multiple preganglionic neurons synapsing with single cell

neuronal divergence

• axons from one preganglionic cell synapsing with numerous cellsin the autonomic nervous system.

divison of motor ans

sympathetic and parasympathetic

parasympatehtic

• maintains homeostasis at rest

• energy conservation and replenishing

Sympathetic

• Prepares body for emergencies

• increased alertness and metabolic activity

“three E’s”: emergency, exercise, or excitement

similarities of sympathetic and parasympathetic

both have autonomic ganglia that house ganglion cells

both use preganglionic neuron and ganglionic to innervate muscles or glands

parasympathetic anatomy

• Preganglionic neuron  in brainstem or S2-S4 spinal cord

• Termed craniosacral division

• Ganglionic neuron innervating muscles or glands

• Preganglionic axons longer than post; few preganglionic axons

• Local response

• Due to long preganglionic neurons with limited branches

Sympathetic anatomy

• Preganglionic neuron in lateral horns of T1-L2

• Termed thoracolumbar division

• Ganglionic neuron innervating muscles or glands

• Preganglionic axons shorter than post; many preganglionic axons

• Usually many structures activated simultaneously

  •  termed mass activation

  • sometimes only single effector activated

• Due to short preganglionic neurons with many branches

• Especially important in response to stress

  • e.g., multiple changes during exercising (incr. HR, BP, breathing rate, pupil dilation, etc.)

Why is parasympathetic activation local and discrete and sympathetic activation able to result in mass activation

Parasympathetic activation is local and discrete due to the long preganglionic neurons with limited branching, allowing for specific target innervation. In contrast, sympathetic activation can lead to mass activation because of shorter preganglionic neurons with many branches, which simultaneously activate multiple structures.

mass activation

A phenomenon where multiple structures are activated simultaneously by the sympathetic nervous system, often during stress or physical activity.

two main ans neurotransmitters

ach and norepinephrine

ach

• Synthesized and released by cholinergic neurons

  • all sympathetic and parasympathetic preganglionic neurons

  • all parasympathetic ganglionic neurons

  • neurons innervating sweat glands and blood vessels of skeletal muscle

Bound by cholinergic receptors (two types): nicotinic and muscarinic

norepinephrine

• Bound by adrenergic receptors

• Synthesized and released by adrenergic neurons

  • most other sympathetic ganglionic neurons

  • form network of swellings at target organ

    • termed varicosities

muscarinic neurons

• Found in: 

  • all target membranes in parasympathetic division

  • selected sympathetic cells 

  • e.g., sweat glands in skin, blood vessels in skeletal muscle

• Different subtypes with different effects

  • either stimulated or inhibited by binding ACh 

nicitonic neruons

• Found on all ganglionic neurons and adrenal medulla

• When bound:

  • open ion channels

  • greater movement of Na⁺ into cell than K⁺ out of cell

  • excitatory postsynaptic potential produced

  • always produces a stimulatory response

alpha receptors

• Typically stimulatory

• α₁ receptors

  • located in most smooth muscle cells => stimulate smooth muscle contraction

  • found in most blood vessels (vasoconstriction), arrector pili, uterus, ureters & internal urethral sphincter

• α₂ receptors

  • inhibit insulin secretion

  • involved with contraction of GI tract sphincters

  • facilitate blood clotting

beta receptors

• β₁ receptors

  • primarily stimulatory

  • found in heart (increase heart rate and force) & kidney (stimulate renin secretion)

• β₂ receptors

  • primarily inhibitory effects

  • in smooth muscle of vessels to heart, liver, and skeletal muscle

  • Lung 

  • uterine and GI tract smooth muscle 

  • detrusor muscle of bladder 

parasympathetic effect on heart rate

decreases heart rate through the release of acetylcholine

synpathetic effect on heart rate

increases heart rate primarily through norepinephrine

parasympathetic effect on smooth muscle of gi tract

increases activity and promotes digestion through the release of acetylcholine

sympathetic effect on smooth muscle of gi tract

decreases activity and inhibits digestion primarily through norepinephrine.

parasympathetic effect on pupil diameter

decreases pupil diameter mainly through acetylcholine

sympathetic effect on pupil diameter

increases pupil diameter primarily through norepinephrine

cooperative effects

• When both parasympathetic and sympathetic produce single result

• E.g., male sexual function

  • penis erect due to parasympathetic innervation

antagonistic effects

• Parasympathetic and sympathetic effects usually antagonistic

• E.g., control of heart rate, control of muscular activity of GI tract, pupil diameter

general functions of endocrine system

• Regulates and controls many metabolic processes

• Helps maintain body homeostasis

  • e.g., maintaining blood glucose levels during erratic food intake

• Serves as one of the two major control systems of the body

  • with the nervous system

endocrine vs nervous system

The endocrine system uses hormones for long-term regulation of body functions, whereas the nervous system uses electrical signals for rapid communication and response.

pineal gland

Pineal secretes melatonin at night

• Causes drowsiness

• Regulates circadian rhythm and has effects on mood

Melatonin influences GnRH secretion

hypothalamus

Hypothalamus hormonally stimulates anterior pituitary to release its hormones

• Hypothalamus secretes regulatory hormones

• Travel via portal blood vessels to pituitary

pituitary gland

Posterior pituitary is storage and release site for oxytocin (OT) and antidiuretic hormone (ADH)

• Hormones made in hypothalamus by neurosecretory cells

  • Packed in secretory vesicles, transported by fast axonal transport

  • Released from synaptic knobs into blood when neurons fire impulses

• Antidiuretic hormone (vasopressin)

  • Functions: decrease urine production, stimulate thirst, constrict blood vessels

• Oxytocin 

  • Functions: uterine contraction, milk ejection , emotional bonding

  • Thyroid-stimulating hormone (TSH)

    • Release triggered by TRH from hypothalamus

    • Causes release of thyroid hormone (TH) from thyroid gland (T3 & T4)

  • Prolactin (PRL)

    • Release triggered by PRH, inhibited by PIH from hypothalamus

    • Causes milk production, mammary gland growth in females

  • Adrenocorticotropic hormone (ACTH; corticotropin)

    • Release triggered by CRH from hypothalamus

    • Causes release of corticosteroids by adrenal cortex

    • Gonadotropins: follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

      • Release triggered by GnRH from hypothalamus

      • In female: regulate ovarian development and secretion of estrogen and progesterone

      • In male: sperm development and secretion of testosterone

    • Growth hormone (GH; somatotropin)

      • Causes liver to secrete insulin-like growth factors 1 and 2

      • GH and IGFs function synergistically to stimulate cell growth and division

thyroid gland

• Cellular transport brings TH into target cells, binds receptor

• T₃ versus T₄

  • Thyroid gland produces more T₄ but T₃ is more active form

  • Most target cells convert T₄ to T₃

• TH increases metabolic rate and protein synthesis in targets

  • Stimulates synthesis of sodium-potassium pumps in neurons 

    • Calorigenic: generates heat, raises temperature

  • Stimulates increased amino acid and glucose uptake

  • Increases number of cellular respiration enzymes within mitochondria

  • Fosters energy (ATP) production

    • Hepatocytes stimulated to increase blood glucose

    • Adipose cells stimulated to increase blood glycerol and fatty acids

      • TH causes  increase in lipolysis and decrease in lipogenesis

      • This saves glucose for the brain (glucose-sparing effect)

    • TH increases respiration rate 

      • To meet additional oxygen demand

    • TH increases heart rate and force of contraction

      • Increased blood flow to deliver more nutrients and oxygen

      • Causes heart to increase receptors for epinephrine and norepinephrine 

parathyroid glands

Contain chief cells and oxyphil cells

• Chief (principal) cells make parathyroid hormone (PTH)

• PTH increases blood calcium 

  • Liberates it from bone, decreases its loss in urine, activates calcitriol hormone

thymus

secrete thymic hormones

• Located anterior to top of heart

• Grows during childhood but shrinks during adulthood

• Maturation site for T-lymphocyte white blood cells

adrenal cortex

• Synthesizes more than 25 corticosteroids

• Three regions producing different steroid hormones:

  • 1. Zona Glomerulosa: Mineralcorticoids (regulate electrolyte levels; ex. Aldosterone)

  • 2. Zona Fasciculata: Glucocorticoids (regulate blood sugar; ex. Cortisol)

  • 3. Zona Reticularis : Gonadocorticoids (sex hormones; ex. Androgens)

adrenal medulla

• Releases epinephrine and norepinephrine with sympathetic stimulation

pancreas

maintain blood glucose

• Normal range is 70 to 110 mg of glucose/deciliter

• High levels damage blood vessels and kidneys

• Low levels cause lethargy, mental and physical impairment, death

testes

testosterone: reproductive organs and various cells
inhibin: anterior pituitary

ovaries

estrogen and progesterone: reproductive organs and various cells
inhibin: anterior pituitary

3 stuctural catergories of hormones

steroids

biogenic amines

proteins

steroids

• Lipid-soluble synthesized from cholesterol

•  Produced in gonads, adrenal cortex

• Calcitriol sometimes classified in this group

biogenic amines

• Modified amino acids

• Includes:

  • Catecholamines  from adrenal medulla, thyroid from thryoid gland

  • Water-soluble except for thyroid hormone

proteins

• Most hormones in this category

• Composed of small chain of amino acids

• Water-soluble

• Includes polypeptides, oligopeptides, glycoproteins

  • e.g., insulin, glucagon, parathyroid hormone, oxytocin, ADH, FSH, TSH

lipid soluble hormones

can diffuse across target cell membrane

• Such hormones are small, nonpolar, and lipophilic

• Their receptors are in the cytosol or nucleus

• Once hormone enters cell it binds to receptor and forms hormone-receptor complex

• The complex binds to a hormone-response element (HRE) of DNA

  • Results in transcription of an mRNA, which is translated to a protein

  • The protein may have structural or metabolic effects

water soluble hormones

use membrane receptors

• Such hormones are polar and can’t diffuse through membrane

• Signal transduction pathway

  • Hormone is first messenger—it initiates events by binding to receptor

  • Binding activates a G-protein (an internal membrane protein that binds a guanine nucleotide)

    • Activation results in binding of GTP instead of GDP

  • G-protein activation causes activation of a membrane enzyme such as adenylate cyclase or phospholipase C

  • Activated enzyme catalyzes the formation of a second messenger—a chemical that modifies cellular activity

local hormones

• Signaling molecules that don’t circulate in blood

• They bind to the cells that release them (autocrine stimulation) or neighboring cells (paracrine stimulation)

eicasionoids

 type of local hormone formed from fatty acids within phospholipid bilayer of membrane

• Synthesized through an enzymatic cascade

prostaglandins

• Stimulate pain and inflammatory responses

• Aspirin and other nonsteroidal anti-inflammatory drugs block prostaglandin formation

autocrine signaling

<span>Type of cell signaling where a cell produces a signal to which it itself responds</span>

paracrine signaling

<span>Type of cell signaling where a cell produces a signal that acts on nearby target cells</span>

up regulation

• increases number of receptors

  • Increases sensitivity to hormone

    • Sometimes occurs when blood levels of hormone are low

    • Sometimes occurs with changes in development, cell cycle, cell activity

down regulation

• decreases number of receptors

  • Decreases sensitivity to hormone

    • Sometimes occurs when blood levels of hormone are high

    • Sometimes occurs with changes in development, cell cycle, cell activity 

synergistic interactions

• One hormone reinforces activity of another hormone

• E.g., estrogen and progesterone effects on a target cell

permissive interactions

• One hormone requires activity of another hormone

• E.g., oxytocin’s milk ejection effect requires prolactin’s milk generating effect

antagonistic interactions

• One hormone opposes activity of another hormone

• E.g., glucagon increases blood glucose while insulin lowers it

pituitary dwarfism

• nadequate growth hormone production

• due to hypothalamic or pituitary problem

• short stature and low blood sugar

pituitary gigantism

• too much growth hormone

• excessive growth and increased blood sugar

• enormous internal organs

• die at early age if untreated

acromegaly

• excessive growth hormone production in adult

• enlargement of bones of face, hands, and feet

• increased release of glucose

• internal organs increased in size

• results from loss of feedback control of growth hormone