Anatomy Lab Practical 2

3 principal divisions of the brain

• forebrain

• hindbrain

• midbrain

parts of the forebrain

• cerebrum

• diecephalon

parts of the cerebrum

• cerebral cortex

• internal structures

cerebrum → parts of the cerebral cortex

• longitudinal fissure

• precentral gyrus

• central gyrus

• postcentral gyrus

• lateral sulcus

• frontal lobe

• parietal lobe

• temporal lobe

• occipital lobe

internal structures → parts of the cerebral cortex

• corpus callosum

• fornix

• basal nuclei

• septum pellucidum

parts of the diecephalon

• thalamus

• hypothalamus

parts of hypothalmus & thalamus

• intermediate mass

• mammillary bodies

• infundibulum

• pituitary gland

parts of the midbrain

• cerebral penduncles

• corpora quadrigemina

sulcus

A shallow depression or groove on the surface of the cerebral cortex

gyrus

The raised ridge or bump between two sulci

fissure

A considerably deeper, larger furrow or cleft than a sulcus

composition of grey matter

• unmyelinated neuronal components

• glial cells

• network of blood vessels

gray matter location

throughout the central nervous system (CNS)

• encompasses the brain and spinal cord

anatomical components of grey matter

• central canal

• ventral (anterior) horn

• laternal horn

• dorsal (posterior) horn

anatomical composition of spinal cord

• spinal nerve (dorsal + ventral ramus)

• dorsal root + ganglion

• ventral root

composition of white matter

• myelinated bundles of axons

• a fatty substance made of proteins and lipids

white matter location

throughout the central nervous system

anatomical components of white matter

• ventral (anterior) fissure

• dorsal (posterior) sulcus

• funiculus (ventral, dorsal, lateral)

white & grey matter in brain vs spinal cord

1. Brain = grey matter on outside & white matter on inside

2. Spinal Cord = grey matter on inside & white matter on outside

nerve vs tract

• NERVE is a bundle of axons in the Peripheral Nervous System (PNS)

• TRACT is a bundle of axons in the Central Nervous System (CNS)

commissure

anatomical location where two structures or tissues join or meet

optic chiasm

an X-shaped neural structure where the optic nerves intersect

cranial meninges

three protective tissue membranes that envelop and support the brain within the skull

3 cranial meninges

• dura mater

• arachnoid mater

• pia mater

dura mater

the outermost, thickest, and most durable of the meninges

• protect the brain and spinal cord

arachinoid mater

the middle, spiderweb-like layer of the meninges

pia mater

the delicate, innermost layer of the meninges

• acts as a protective barrier and blood vessel network for the CNS

ventricles of the brain

• lateral ventricle

• choroid plexus

• third ventricle

• fourth ventricle

• cerebral aqueduct (communicate btw 3rd ad 4th ventricles)

lateral ventricle

C-shaped cavities located within the cerebral hemispheres of the brain

• responsible for production, circulation, and containment CSF to protect the brain

choroid plexus

network of specialized cells and blood vessels located within the brain's ventricles

• produce cerebrospinal fluid (CSF) and form the blood-CSF barrier

third ventricle

situated between the right and left halves of the thalamus and hypothalamus

• produces, cushions, and circulates cerebrospinal fluid (CSF)

fourth ventricle

located between the brainstem and the cerebellum

• a crucial passageway that allows CSF to flow out brain's internal cavities and into the protective spaces around the CNS

cerebral acqueduct

a narrow, fluid-filled tube located in the midbrain

• allows CSF to flow directly from the third ventricle to the fourth ventricle

CN I

olfactory nerve

CN I function

transmit sensory info about smell and odors

CN II

optic nerve

CN II function

transmit sensory visual info from retina to brain

CN III

oculomotor nerve

CN III function

control eye movement, pupil size, and shape

CN IV

trochlear nerve

CN IV function

control superior oblique muscles of the eye

CN V

trigeminal nerve

CN V function

give sensory info to face, scalp, teeth and mouth for chewing

CN VI

abducens nerve

CN VI function

control lateral rectus muscles of the eye

CN VII

facial nerve

CN VII function

controlling motor, sensory and parasympethetic functions

2 branches of CN VIII

1. vestibular branch

2. cochlear branch

vestibular brach (CN VIII)

transmit vital spacial, gravitational, and movement signals from the inner ear to the brain

cochlear branch (CN VIII)

transmit auditory signals to the brain

CN IX

glossopharyngeal nerve

CN IX function

swallowing, taste, salivation, and gag reflex

CN X

vagus nerve

CN X function

heart rate, digestion, and immune reponses

CN XI

accessory nerve

CN XI function

control nexk and shoulder movement, and vocal cord function

CN XII

hypoglassal nerve

CN XII function

control all movement of the tongue

what cranial nerves DO NOT exit from the brainstem

1. CN I → olfactory nerve

2. CN II → optic nerve

what nerves provide parasympathetic innervation to a target

1. CN III → oculomotor nerve

2. CN VII → facial nerve

3. CN IX → glossopharyngeal nerve

4. CN X → vagus nerve

components of the CNS

• brain

• spinal cord

what system is a “nerve” a part of

the PNS

where does a nerve begin

as it enters through the intervertebral foramen

spinal nerve type

a MIXED nerve

• contains both sensory & motor components

4 spinal plexuses

• cervical plexus

• brachial plexus

• lumbar plexus

• sacral plexus

cervical plexus

• innervates upper body (head, neck, shoulders, diaphragm)

• major nerve = PHRENIC NERVE

brachial plexus

• innervates the upper limbs

• major nerve = MEDIAN NERVE

lumbar plexus

• innervates the thigh

• major nerve = FEMORAL NERVE

sacral plexus

• innervates the lower limb and glutes

• major nerve = SCIATIC NERVE

frog dissection → corneal reflex

• still works even when forebrain removed

• DOES NOT work when hindbrain is removed

• DOES NOT work when spinal cord is cut

frog dissection → swimming movement

• still works even when forebrain removed

• DOES NOT work when hindbrain is removed

• DOES NOT work when spinal cord is cut

frog dissection → posture

• still works even when forebrain removed

• DOES NOT work when hindbrain is removed

• DOES NOT work when spinal cord is cut

frog dissection → breathing

• still works even when forebrain removed

• DOES NOT work when hindbrain is removed

• DOES NOT work when spinal cord is cut

frog dissection → tongue muscle tone

• still works even when forebrain removed

• DOES NOT work when hindbrain is removed

• DOES NOT work when spinal cord is cut

frog dissection → righting reflex

• still works even when forebrain removed

• DOES NOT work when hindbrain is removed

• DOES NOT work when spinal cord is cut

frog dissection → acid reflex

• still works even when forebrain removed

• STILL WORKS even when hindbrain is removed

• DOES NOT work when spinal cord is cut

frog dissection → withdrawl reflex

• still works even when forebrain removed

• STILL WORKS even when hindbrain is removed

• DOES NOT work when spinal cord is cut

pupil constriction controlled by

parasympathetic nervous sytems

• uses acetycholine

effector mediating pupil constriction

sphincter pupillae of the iris

pupil dilation controlled by

sympathetic nervous system

• uses epi/norepi

effector mediating pupil dilation

dilator pupillae of the iris

types of spinal reflex tests

1. patellar (knee-jerk) reflex test

2. achilles tendon (ankle-jerk) reflex

what are spial reflexes also called

stretch reflexes

• because the hammer tap stretches a muscle/tendon

• concidered protective readjustments because the response prevents muscle/tendon overstretching

patellar (knee-jerk) reflex test

this test assesses spinal motor neurons in L2-L4

• a rapid, involuntary stretch reflex

patellar (knee-jerk) reflex test COMPONENTS

• stimulus → tap on patellar tendon with a hammer

• receptor → muscle spindles in quadricep

• effector → quads recieve signal from motor neurons to stretch

• response → kicking/extending leg motion

hyporeflexia

less than normal response to patellar tendon tap

hyperreflexia

more than normal response to patellar tendon tap

achilles tendon (ankle-jerk) reflex

assesses spinal motor neurons at S1 level

• deep tendon reflex

achilles tendon (ankle-jerk) reflex COMPONENTS

• stimulus → tap to achilles tendon with hammer

• receptor → muscle spindles in calf muscles detech sudden stretch and fire signals

• effector → gastrocnemius + soleus muscles recieve signal and carry out movement

• response → involuntary, rapid contraction of calf muscles which cause foot to jerk downward

general sensory tests

1. two-point descrimination test

2. adaption of tactile pressure receptors

3. adaptation of temperature (thermal) receptors

4. radiating pain

two-point descrimination test

assesses the sensitivity of different skin areas by asking subjects if they feel two objects or one, on different areas of the skin

two-point descrimination test SENSORY PATHWAYS

ascending sensory afferent pathway

• dorsal column-medial lemniscus pathway

• 1st, 2nd, 3rd order neurons

areas MOST SENSITIVE in two-point descrimination test

• fingertips

• lips

• tongue

adaptation of tactile pressure receptors test

uses classic constant stimulus coin method

• seeing how long it takes for the brain to ignore a constant, steady pressure

adaptation of tactile pressure receptors test MECHANISM

measures how quickly rapidly adapting receptors like Meissners and Pacinian corpuscles stop firing when a stimulus remains constant

• slowly adapting receptors (like Merkel discs) continue to fire

cutaneous receptors activated at ONE COIN

uses superficial, rapidly adapting mechanoreceptors because the pressure is minimal (less time to adapt)

• EX: meissners corpuscles

cutaneous receptors activated at FOUR COINS

increased pressure deforms deeper mechanoreceptors because its a new/stronger stimulus (longer duration to adapt)

• EX: pacinian or ruffini corpuscles

sensory adaptation

an automatic process which our sensory receptors become less respnsive to constant, unchanging stimului

• allows brain to filter inputs to focus attention to novel or threatening changes

adaptation of temperature (thermal) receptors test

shows how sensory nerves adjust to a constant stimulus

• overtime the receptors reduce theie firing rate, causing hot and cold sensationg to fade

adaptation of temperature (thermal) receptors test RESULT

aone hand was submerged in hot water and the other in cold water for 2 min and then you put both in room-temp water

• the hot water hand will feel COLD in room-temp water

• the cold water hand will feel HOT in room-temp water