Exam 2: Brainstem and Cerebellum Flashcards
Brainstem
- consists of mesencephalon (midbrain), pons, medulla oblongata
- relay center for sensory input and motor output
- also responsible for many basic reflex actions
Pyramids
- bilateral ridges on anterior (ventral) side of medulla oblongata
- motor axons
- most of these axons desussate (cross over to opposite side)
- so in most instances each side of brain controls opposite side of body
Autonomic Nervous System Centers (part of what)
- part of medulla oblongata
- cardiac center: regulates heart rate
- vasomotor center: constricts and dialates arterioles so it regulates bp (constrict=increased bp, dialate=decreased bp)
- respiratory center: regulates breathing rate
- other centers
Inferior Part of 4th Ventricle
-space inside medulla oblongata
Pons
- chiefly composed of groups of axons (nerve fiber tracts)
- middle portion of brainstem
Respiratory Centers
-in pons help to control rate and depth of breathing
Superior Part of Fourth Ventricle
- part of pons
- continuous with cerebral aqueduct
Tectal Plate
- on posterior side of mesencephalon
- divided into superior colliculi and inferior collicui
Superior Colliculi
- (2) visual reflex centers
- coordinate head and eye movements to sudden image
Inferior Colliculi
- (2) auditory reflex centers
- coordinate head and eye movements to sudden sound
Cerebral Peduncles
- part of mesencephalon
- groups of axons (nerve fiber tracts) on anterior side of mesencephalon
- conduct nerve impulses between cerebrum and brainstem
Cerebellum
- right and left cerebellar hemispheres
- not part of brainstem
- higher motor and sensory functions
Cerebral (Mesencephalic) Aqueduct
-connects 4th ventricle to 3rd ventricle
Cerebellar Peduncles Definition
-groups of axons (nerve fiber tracts)
Inferior Cerebellar Peduncle
-connect medulla oblongata to cerebellum
Middle Cerebellar Peduncle
-connect pons to cerebellum
Superior Cerebellar Peduncle
-connect midbrain to cerebellum
Functions of Cerebellum
- coordinates and fine tunes skeletal muscle movement (cerebrum initates the movement, but the cerebellum makes it pretty)
- maintains balance and posture in response to info from proprioceptors (sensory nerve endings in muscles, joints, and tendons)
- DOES NOT START SKELETAL MUSCLE MOVEMENT
Cranial Meninges
- Pia Mater
- Subarachnoid space
- Arachnoid matter
- Dura Mater-outermost layer
- Inner Meningeal Layer
- Outer periosteallayer
- (in order from deepest to most superficial)
- in some areas the layers are separated and form dural venous sinuses
Dural Venous Sinuses
- large veins that drain blood away from vein
- between inner menigeal and outer periosteal layers of dura mater
- vein walls formed from dura mater
CSF
- cerebrospinal fluid
- provides buoyency for brain and spinal cord
- maintains CNS chemical environment
- produced continuously (approx 500 mL/day)
Ventricular System Consists of
- 1 & 2) left and right lateral ventricles: found in each cerebral hemisphere
- 3) third ventricle: space in diencephalon connects to each lateral ventricle via an interventricular foramen
- 4) cerebral aqueduct: in mesencephalon
- 5) fourth ventricle: in pons and medulla oblongata.
- (CSF flows from 1-5)
CSF Circulation Process
- CSF produed by choroid plexus in ventricles
- CSF flows from third ventricle to cerebral aqueduct to 4th ventricle
- CSF leaves 4th ventricle and enters subarachnoid space
- CSF circulates in subarachnoid space
- Excess CSF removed from subarachnoid space by arachnoid villi
- Pressure in subarachnoid space opens ‘flap’ in a villus so excess CSF leaves the subarachnoid space and enters dural venus sinuses (bloodstream)
Arachnoid Villi
-extensions of arachnoid mater that project int dural venous sinus
Hydrocephalus
- CSF production begins to exceed its removal or drainage at arachnoid villi
- ‘water on the brain’
- head becomes enlarged in young child
- fluid buildup can compress brain unless a medical shunt is put in.
