Human Bio Exam 3

Joints

articulating - bone to bone contact point

Classification of Joints (articulations)

Classification based on structure

1. Fibrous joints

• dense connective tissues connect bones

• bones in close contact

2. Cartilaginous joints

• hyaline cartilage or fibrocartilage connect bones

• boney joints may form when fibrous or cartilaginous joints ossify

3. Synovial joints

• most complex

  • joint capsule

  • synovial fluid

  • reinforcing ligaments and cartilage

Classification based on function

1. Synarthrotic joints → fibrous & cartilaginous

• immobile

2. Amphiarthrotic joints → fibrous & cartilaginous

• slight mobility

3. Diarthrotic joints → synovial

• free mobility

Synovial Joints: General Structure

• Articular cartilage → reduce friction

  • only on articulating surface

  • watery matrix

  • similar to hyaline cartilage

• joint capsule

  • fibrous outer layer:

    • dense connective tissue connecting to periosteum

  • synovial membrane:

    • inner surface, areolar tissue and incomplete epithelium.

    • produce synovial fluid

  • synovial fluid

    • produced by synovial membrane

    • within joint cavity

    • viscous

    • lubricant, shock absorption, nutrient distribution

Accessory Structures of Synovial Joints

• meniscus/ menisci

  • fibrocartilage: additional layer between articulating bones

  • shock absorption

  • subdivide cavity, channel fluid, alter shape of articulating surface

• Fat pads

  • adipose covered by synovial membrane

  • protect articular cartilage

  • packing material

• Bursa

  • pockets of synovial fluid surrounded by membrane

  • reduce friction at site of tendon and ligament attachment

Proprioceptors 

Monitor position and movement of skeletal muscle and joints 

• muscle spindles

  • specialized muscle fibers throughout a muscle (neighbor regular muscle cells)

  • sarcomeres on either end of a regoin without filaments (wrapped by sensory neurons

  • respond when muscle is stretched

• golgi tendon organs

  • sensory dendrites interwoven among collagen fibers of tendons

  • provide info about contraction of tendons

  • tendon stretch→ squeeze sensory dendrites → inform brain of activation

• Joint capsule receptors

  • mechanoreceptors found on sensory dendrites in joint capsule

  • found in synovial membrane

  • responds to pressure, stretch, and movement

    • eg pacinan corpsucles and ruffini endings

Ligaments and Tendons 

• ligaments attach bone to bone

  • more flat

  • slightly less dense

• tendons attach muscle to bone 

  • more round

  • more dense

• attach via fibrocartilage transition to periosteum 

• dense regular connective tissue 

  • thick parallel bundles of collagen

Accessory structures of knee

• medial and lateral menisci

  • fibrocartilage pads between femur and tibia

• fat pads

• anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL)

  • femur to tibia

  • limit anterior/posterior movements

• medial collateral ligament (MCL) and lateral collateral ligament (LCL)

  • stabilize knee in standing position

Unhappy triad of injuries

tears/rupture of all 3:

• ACL

• MCL

• lateral meniscus 

• caused by string force outside of knee when foot is stationary 

treatment: ACL tear commonly requires a graft 

Divisions of nerous system

• Central Nervous system 

  • Brain

  • Spinal cord

• Peripheral Nervous System 

  • All nervous tissue other than CNS 

  • Nerves: transmit information to and from CNS

Cranial and Spinal Nerves

• Cranial Nerves

  • arise from brain

  • 12 pairs on each side → 24 total

• Spinal Nerves

  • arise from spinal cord

  • 31 pairs

Organization of Peripheral Nervous System

• Afferent → CNS → Efferent

Afferents (sensory) accepting

• Somatic Sensory Neurons: skin, skeletal muscle, joints

• Special Sensory Neurons: smell, taste, vision, hearing, balance (vestibular sense)

• Visceral Sensory Neurons: internal Organs 

→

Central Nervous System 

→

Efferents (motor) enacting

• Somatic Motor Nervous System (SNS):

  • skeletal muscle contraction 

  • controlled

• Autonomic Nervous System (ANS)/ Visceral Nervous System:

  • smooth/cardiac muscle, glands, adipose 

  • uncontrolled

    • Sympathetic Nervous System

      • Stress Response

    • Parasympathetic Nervous System 

      • rest and digest response

Functions of Spinal Cord and Nerves

1. Transmission of sensory information to brain (afferent/sensory)

2. Transmission of motor information from brain (efferent/motor) 

3. Generation of spinal reflexes REVIEW EARLY

Gross Anatomy of Spinal Cord

• leaves cranium at foramen magnum → extends into vertebral canal 

• true spinal cord ends at L2 vertebra

• Spinal cord in adult ends at level of 1st lumbar vertebra 

1. cervical enlargements:

• supplies nerves to arms

2. lumbar enlargement:

• supplies nerves to legs

3. conus medullaris:

• tapering of spinal cord to a point below lumbar enlargement 

4. Filim Terminale (not neuronal):

• connective tissue that connects conus → coccygeal ligament (full length of vertebral column)

  • for stabilization

5. Cauda equina:

• bundle of spinal nerve roots and filim terminal within vertebral canal from ~ L2 - S5

Cross Section of Spinal Cord

• posterior median sulcus in front

  • little groove

• anterior median fissure at bottom 

  • larger groove

• Central canal

  • filled with CSF

• Inner gray Matter:

  • abundance of cell bodies/dendrites (inner, deep)

• Outer white matter:

  • abundance of myelinated (and some unmyelinated) axons (outer, superficial)

Roots → where spinal nerves communicate with spinal cord

• Ventral roots:

  • Efferent (motor) pathways: carry information away from CNS → periferal targets 

• Dorsal Roots:

  • Afferent pathways: carry sensory information from periphery → CNS

from spinal cord into dorsal 

ganglion: collection of cell bodies of peripheral nervous system 

Ventral root join with dorsal root → form spinal cord 

Organization of White and Gray Matter

Gray Matter:

• cell bodies + dendrites 

• organized into nuclei = collection of cell bodies in CNS

• dorsal horns: (sensory)

  • somatic and visceral sensory nuclei

  • process/ relay sensory information 

• ventral horn: (motor)

  • efferent 

  • somatic motor nuclei 

  • integrate / relay motor information 

• Lateral horns: (motor)

  • thoracic and lumbar only

  • visceral motor nuclei

White Matter

• organized into columns

• anterior, posterior, and lateral columns

• each column contains tracts

• Tracts = bundles of axons with similar structure and function

  • relay info up and down spinal cord.

Commissures: both white and gray, axons which cross sides 

Associated Structures: Meninges

Function: provide structural support, shock absorption, house blood vessels

• Epidural space:

  • between vertebrae and dura mater

  • areolar and adipose tissue 

• Dura mater

  • outer layer

  • dense collagen fibers longitudinally along SC

• Arachnoid mater

  • thin epithelial membrane

  • connected to subarachnoid space (has cobweblike structure)

• Pia mater:

  • inner layer

  • collagen and elastin

  • physically attached to nervous system

Meningitis

• inflammation of meninges 

• disrupt flow of CSF 

• damage neurons in affected areas 

Epidural Anesthesia and Spinal Taps

Epidural Anesthesia

• Administration of anesthetics to epidural space within lumbar region of vertebral column

• Pain reducing effect only on nerves in that area

Lumbar Puncture/ spinal tap

• sampling of CSF

• Reducing CSF pressure

• Site: subarachnoid space within lumbar region of vertebral column

Spinal Nerves and Spinal Cord

• 31 pairs of spinal nerves (junction of dorsal and ventral roots)

• innervate neck, truck, upper, and lower limbs

• grouped by level and numbered

  • Cervical Nerves: C1-C8

  • Thoracic Nerves: T1-T12

  • Lumbar Nerves: L1-L5

  • Sacral Nerves: S1-S5

  • Coccygeal Nerve: Co

• Most exit vertebral column via intervertebral foramina

Dermatomes 

Area of skin innervated by nerve fibers of a particular pair of spinal nerves

Shingles: variant of chicken pox 

•  attacks neurons within the dorsal root of spinal nerves 

• painful rash and blistering 

• follows the dermatomes of affected spinal nerve

Structure of Peripheral Nerves 

Nerves contains axons of many individual neurons 

• Endonurium

• perinurium

  • isolates fascicles 

• endoneurium 

  • in fascicle, isolate axons. 

spinal nerves are mixed nerves

• contain efferent + afferent fibers (motor information + sensory information) 

• branch at later points 

Branches (Rami) of Spinal Nerves

spinal nerves branch into

• dorsal branch (ramus) of spinal nerve 

  • small

  • innervates narrow strip of muscles 

  • heads back torwards

• Ventral branch (ramus) of spinal cord

  • large innervates lateral and anterior trunk and limbs

sensory info happens along vertebral

front = ventral

dorsal = back

Spinal Reflexes

Reflex= rapid, unconscious responses to specific stimuli

• reflexes are programed → once activated, produce same response

• each reflex follows same 5 step reflex arc → circuitry of single reflex 

reflex arc 

1. arrival of stimulus → act

Patelar Reflex

• monosynaptic response (1 synapse) 

• receptor: muscle spindle (proprioceptors) 

• Sensory Neuron: stretch activates neurons that innervate muscle spindle 

• Motor Neuron: sensory neuron directly synapses with motor neuron in spinal cord 

• Effector: muscle fibers in region of spindle contract in response to action potentials from motor neurons 

Crossed Extensor Reflex

eztension of the opposite limb

Activation of sensory neuron →

• ssstimulation of excitatory motor neurons to extensor muscle on opposite limb 

• stimulation of inhibitory interneurons to flexor on opposite limb 

• CONTRALATERAL reflex arc → crosses to other side

note: simple stretch and withdrawal reflexes activate isolateral reflex arcs → same side of the body

Structure and Function of Brain

Embryonic Development of the CNS

nervous system develops from ectoderm

• 14 days = dorsal streak appears along length of embryo → thickens to form neural plate

• 18 days: neural plate sinks to form neural groove and neural fold

  • neural crest cell = ectodermal cells that lie along edge of neural fold  

• 21 days: neural fold fuses along midline → create hallow neural tube 

  • give rise to most neurons and glial cells of CNS (not microglia) 

• neural crest cells → PNS

  • neural crest cells separate from neural tube → create longitudinal column of cells 

  • gives rise to meninges and most of PNS

ectoderm → skin and nervous system 

Further embryonic development

Overview of adult brain regions

• cerebellum 

Pathway of CSF flow

• CSF circulates through ventricles, aqueduct, and centra canal

• enters subarachnoid space via apertures (holes) within the fourth ventricle that pump csf 

• CSF is drained into the venous blood (dura sinuses) via arachnoid granulations 

entire volume of CSF = 150 mL

CSF is constantly being produced → 500 mL/day

Entire volume of CSF is turned over 3 times/day

Brain stem

includes: midbrain, pons, medulla oblongata

• connects spinal cord to rest of brain → pathway for ascending and descending tracts 

• site of control for many process that regulate life sustaining function (autonomic)

• most cranial nerves connect to brain stem 

• have cell bodies for most dopaminergic, serotonergic, adrenergic, and cholinergic neurons 

  • → role in attention/consciousness and habituation, mood, movement, motivation 

Medulla Oblongata

• pyramids: relay voluntary motor commands from HIGHER centers → spinal cord

• olives: relay motor commands from HIGHER centers → cerebellum

• Reflex centers of Medulla → receive and integrate input from sensory nerves and other brain regions

  • cardiac control centers: heart rate, strength of heart contraction

  • vasomotor control center: blood vessel dilation

  • respiratory control centers: rate and depth of breathing

Pons

• major function → linking cerebellum to higher brain centers and spinal cord

  • Transverse fibers: link 2 hemispheres of cerebellum

• continuation of sensory/motor tracts connecting higher and lower centers and nuclei of cranial nerces

• Reflex centers of pons:

  • 2 additional respiratory control centers

  • mictujhjwehrkuwhrkwehrkehwhrewiuewuke

Midbrain

• cerebral peduncles of midbrain: (ventral lateral portion)

  • location of mostly descending tracts → cerebellum or SC

• Tectum of Midbrain (posterior to cerebral aqueduct)

  • Corpora quadrigemina: process auditory and visual sensations → generate reflex movements (head, body, eyes)

    • superior colliculus: visual stimuli

    • inferior colliculus: auditory stimuli

• Tegmentum of midbrain (anterior to cerebral aqueduct)

  • location of structures important for motor control

    • Red nuclei = connections to cortex and cerebellum → unconscious motor commands

    • substantia nigra: connections to basal nuclei → normal inhibition of unconscious movement

Cerebellum

Right+ left hemisferes conected by transverse 

body position and motor related tasks

integrates senstor

structure:

posterior to pons and medulla 

• separated in two hemispheres connected by vermis (posterior)

• outer gray matter: cerebellar cortex

  • purkinje cells: extensive dendrites (200,000 synapses) → gray matter of cerebellum  → MOTOR CONTROL

• inner which matter: arbor vitae

• 3 large nerve tracts (peduncles) connect cerebellum to other brain regions: superior, middle, inferior 

Diencephalon: Thalamus

Sensory process relay station

• important function as sensory relay

• thalamic nuclei receive a mority of sensory information (except olfaction)

• projections to the appropriate sensory cortex

  • filtering effect → minority of arriving sensory information is passed on 

Numerous 

Diencephalon: Hypothalamus

Homeostatic regulation of multiple body functions

Nuclei seperately regulate

• autonomic functions (influence automatic brainstem functions)

FFF: feeding fighting fucking

Diencephalon: Epithalamus

anterior: poertions

Limbic System

border between diencephalon + cerebrum: nuclei + tracts

c. amygdala

• relay between: cerebrum , limbic system, sens

Cerebrum: white + gray matter

gray: cerebral cortex (outside)

White matter: cerebrum

A) association fibers

• different regions of the same hemisphere

B) projection fibers

• ascending + descending

Grey: basal nuclei → subcortical nuclei

a. caudate nucleus

b. putamen

c. globus pallidus

→ connect with cereb

hemispheric lateralization

Sulci: dividing cerebrum hemispheres

Cerebral cortex functional regions

sensory areas: one for each sense (already filtered by thalamus)

Motor Areas

Association Areas: takes raw data from primary cortex and assigns meaning to ut

Integration Areas: takes info from multiple senses and puts together

Cranial Nerves

KNOW SENSORY MOTOR OR BOTH

I. Olfactory

• sensory → smell impulses via olfactory foramina

II. Optic Nerve

V. Trigeminal (MIXED)

• wewew

VI. Facial (MIXED)

• sensory from taste

VII. Glossopharyngeal

• tastes

Somatic Motor Nervous System

• efferent neurons

  • originate in brain, travel to facilitate

decussation

axons of most motor tracts must CROSS THE MIDLINE of spinal cord or brainstem to other side

Corticospinal tract (somatic motor)

voluntary skeletal muscle movement

1. upper motor neurons descend vuia cerebral peduncles to → pyramids of

Autonomic Motor System (

unconscious maintainance of life support + homeostasis

Hypothalamus: control center for autonomic activity (4 Fs)

→

Motor Pathways: regulate glands, smooth muscle, cardiac muscle, adipose

Divisions of ANS: sympathetic (fight or flight)

ANS: parasympathetic (rest and digest)

decreases:

• metabikuc rate

• Heartrate

• blood pressure

increases

Autonomic nervous system working together

SNS and PNS have opposing affects

preganglionic neuron is SHORT

postganglionic neuron is LONG

cell bodies of preganglionic sympathetic neurons originate in lateral gray horns of T1-L2

Travel via Communicating Rami

• connect spunal nerves ti sympathetic trunks, contain sympathetic axons

• travel to white ramus

(for sympathetic nervous system)

SNS + sympathetic chain ganglia

Pathway for preganglion neuron T1-L2 only

• cell body in lateral gray hirn

2 paths:

1. cell body in sympathetic chain ganglia, follows GRAY ramus to → spinal nerve

SNS + collateral ganglia

pre-gang pathway:

• cell body in lateral gray horn

• exists spinal cord via ventral root, joins spinal cord

• follows white ramus to sympathetic ganglion

SNS + adrenal gland

NO SYNAPSE ON ANY GANGLIA

pre-gang pathway:

• exis

80% epinephrine (adrenaline)

20% norepinephrine

Summary of SNS and PNS

Both use acetyl choline

norepinephrine released by post ganglionic fiber is sympathetic nervous system

neuroendocrine found in adrenal glands 

epinephrine = more potent form of norepinephrine 

spread throughout bloodstream to have wide affect

all alpha and beta receptors recognize norepinephrine and epinephrine 

heart has beta receptors

PNS organization:

• PREganglionic neuron is LONG

• POSTganglionic neuron is SHORT

III. oculomotor → contraction of iris/lens

VII. mucus + saliva production f

IX. saliva production

X. all PNS in thoracic + abdominopelvic cavity

ANS: neuroeffector junction

Neurotransmitters of the ANS

Ach → acetylcholine released by choluinergic neurons

NE relwased nu adrenergic neurons

ALL pregang neurons are cholinergic (PNS, SNS)

• parasympathetic pathways

Neurotransmitor receptors

nicotinic receptors:

N1 (skeletal muscle), N2 (postgang)

muscarinic

norepenephrine

(effectors on sympathetic nervous system)i e

Alpha recpetors

Sensory Receptors

goal of each sensory receptor is TRANSDUCTION

general sensory receptors 

• exterorecreptors: external stimuli

  • mechanoreceptors: touch, pressure, vibration 

  • thermoreceptors: temperature

  • nociceptors: pain and itch 

• proprioceptors: positional and movement of skeletal muscle

  • muscle spindle, golgi tendon orgon, joint capsule receptors

• interoreceptors: internal stimuli 

  • baroreceptors: monitor pressure in hollow organs

  • chemoreceptors: detect pH, CO2, O2

  • nociceptors: pain

Specialized Sensory Receptors

• vision

  • photoreceptors

Common Receptors 

• Mechanoreceptors

  • ex. tactile/touch receptors, muscle spindle, baroreceptors, mechanoreceptors of inner ear

• Ionotropic: Chemically gated ion channels 

  • changes structure of protein to open

  • ex: nociceptors 

• Metabotropic: G-protein coupled receptors 

  • ex: photoreceptors, olfactory/taste receptors 

General Sensory Pathways: Touch, Pressure, Pain, Temperature

• somatic sensory pathways:

  • First order neuron→ delivers sensory information to CNS (ie: cell body in DRG or cranial nerve)

  • Second order neuron → cell body of interneuron within spinal cord/brain

  • Third order neuron → cell body of interneuron within thalamus

  • synapse on neurons of primary somatosensory cortex

first neuron synapsing on the second neuron travelling up posterior column into medulla oblongata

spinothalamic pathway: anterior tract → crude touch, pressure

spinothalamic PAthways

latera

Proprioceptive input

Proprioceptuve input

• first order neuron → synapses in dorsal horn on

• sedond order neuron → axons in lateral columns (spinocerebellar pathway) and synapse directly in cerebellum

  • 2 divisions: within lateral column, contralateral and isolateral

  • does not enter consciousness

• both sides cross ober

General sensory pathways: Visceral Input (interoceptors

Visceral Input (interoceptors)

• first orfer neuron → axons typically follow pathway od autonomic motor neurons in reverse to spinal cord/cranial nerve

  • thesoathways are often complex

  • most major thoracic/abdominal organs send sensory info back via vagus nerve to synapse on

Organization of the retina

layers

• pigmented retina:

  • pigmented epithelial cells

• neural retina

  • photoreceptors (rods and cones) synapse on

  • → bipolar cells

  • → ganglion cells: axons that make up optic nerve

• process starts from back to front

  • light bounces off back of eye, travel through rods and cones → bipolar cells → ganglion

Photoreceptors

• Rods: highly light sensitive (no color)

  • densely scattered in peripheral retina

• Cones: visualize color

  • 3 types: red, green, blue (require more light)

  • highly concentrated in fovea

  • specific wavelenths

• outer segment: series of membranous disks within photoreceptors

  • contains the visual pigments

Visual Pigments

absorb photons of light (first step of visual transduction)

• found within membranes of outer segments

• consist of pigment (retinal)

• bound to a protein (opsin)

• pigment is always retinal

• protein in always opsin

  • type of opsin determines wavelength sensitivity

  • 1 opsin for rods

  • 1 for each type of cone

• visual pigment in rods is rhodopsin

Visual transduction (resting state)

rods in the darkk

• chemically gates Na+ channels are open

  • bound to cGMP

• membrane potential: -40mV

• continuously releasing neurotransmitter onto biopolar cells

• cGMP keeps channels open to let Na+ enter cell to make it less negative

visuawl transduction —> activation

rhodosin is a G-protein coupled receptor (GPCR)

• step 1

  • retinal absorbes a photon

  • converst from 11 cis to 11 trans

  • acticates opsins

• step 2

  • opsin activates transduction

  • transucin activates pjospjodoesteraseeeee

  • cG<P-

olfaction

olfaction and taste are chimical senses; chemical binding a receptor

• odorant molecules must be volatile and dissolve through nasal mucosa to reach olfactory epithelium wjcoh contains receptor celod

olfactory recptors

~ 350 human

• a receptor can be sensitive to a class or several couses of molecurx

NOT TESTED ON OLFACTORY OSTHESY'

Taste Anatomy

• tongue papillae found along edge of tongue

back 1/3 of tongue → hypoglossopalangeal nerve

• front 2/3 of tonue → facial nerve

taste buds are also located in soft palate and within epithelium of pharynx

Taste Qualities

• each taste cell is responsible to only one taste quality

• each taste bud is responsible to all taste qualities

• tastants dissolve in saliva and are carried to taste bud through taste pore

• qualities

  • sweet, sour, salty, bitter, umami

  • others: fat, metallic, calcium, water

• flavor is a combination of many senses→ taste, olfaction,

• spicy and cooling effects of food are due to activation of pain and temperature receptors on free nerve endings of CN V called chemesthesis (trigeminal sense)

Taste Transduction - salty, sour

salty and sour taste

• salt (Na+) and sour (H+) can directly depolarize taste cells via cation pores

  • H+ and Na+ do not pass through same channels (pores)

  • sour channel

    • proton channel

  • salt channel

    • epithelial sodium channel (ENaC)

    • non-sodium specific channels

Taste Transduction - sweet, bitter, umami

sweet, bitter, umami ligands bind GPCRs

• 2 famililies of taste GPCRs

• T1Rs: 3 members

  • umami - T1R1 and T1R3

  • sweet - T1R2 and T1R3

• T2Rs: 25 members

  • bitter

Anatomy of the Ear

NO INFO ON EXAM 3 but on final

anatomy of ear

Equilibium

• sound funneled through auriccle into external acoustic meatus

• →tympanic membrane (eardrum)

• head of snail = vestibule

• cochlea = snail shell

• antenae = semicircular canals