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Brain. Meninges, ventricles, cerebrospinal fluid & blood supply Hindbrain and midbrain Forebrain Limbic system. Brain Description. Brain weighs 3 to 3.5 pounds Major portions -- brainstem, cerebrum, and cerebellum cerebrum is 83% of brain volume

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Brain l.jpg
Brain

  • Meninges, ventricles, cerebrospinal fluid & blood supply

  • Hindbrain and midbrain

  • Forebrain

  • Limbic system


Brain description l.jpg
Brain Description

  • Brain weighs 3 to 3.5 pounds

  • Major portions -- brainstem, cerebrum, and cerebellum

    • cerebrum is 83% of brain volume

    • ___________________ contains 50% of the neurons


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Brain

Longitudinal fissure separates 2 cerebral hemispheres.


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Meninges

  • Dura mater

    • outer periosteal layer

    • inner meningeal layer

    • dural venous sinuses

    • dural septa

      • falx cerebri, falx cerebelli and tentorium cerebelli

    • dural hemorrhages

  • Arachnoid mater

  • Pia mater



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Ventricles and Cerebrospinal Fluid

  • Internal chambers within the CNS

    • lateral ventricles

    • third ventricle

    • cerebral aqueduct

    • fourth ventricle

    • central canal of spinal cord

  • Lined with ependymal cells and contains ______



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Cerebrospinal Fluid

  • Clear liquid fills ventricles and canals & bathes its external surface ________________________

  • Brain produces & absorbs about 500 ml/day

    • filtration of blood through choroid plexus

    • has more Na+ & Cl- but less K+,Ca+2, and proteins than plasma

  • Functions (3)

    • Buoyancy, protection, and chemical stability

  • Escapes from 4th ventricle to subarachnoid space

  • Drains from _________________________ into venous sinus



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Blood-Brain and Blood-CSF Barriers

  • BBB - endothelium & perivascular astrocyte feet

    • permeable to lipid-soluble materials (alcohol, O2, CO2, caffeine, nicotine and anesthetics)

    • administer drugs through nasal sprays

    • Circumventricular organs – breeches in the system

      • Hypothalamus, Post. pituitary, Pineal, & Choroid plexus

      • monitoring of glucose, pH, osmolarity & others

      • may allow route for HIV virus to invade the brain

  • Blood-CSF barrier - choroid plexus is ependymal cells joined by _________________________



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Medulla Oblongata

  • 3 cm long

  • Ascending & descending tracts

  • CN nuclei (VIII, IX, X, XI, XII)

  • Nuclei for somatic and visceral sensory; somatic cerebellar relay

  • Cardiac, vasomotor, & respiratory centers

  • Reflex centers for coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, and movements of the tongue and head



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Pons

  • Bulge in the brainstem, rostral to the medulla

  • Ascending sensory tracts

  • Descending motor tracts

  • Pathways in & out of cerebellum - peduncles

  • Nuclei concerned with sleep, hearing, balance, taste, eye movements, facial expression, facial sensation, respiration, swallowing, bladder control & posture

    • cranial nerves V, VI, VII, and VIII


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Cerebellum

  • Connected to brainstem by cerebellar peduncles

  • White matter _____________________

  • Folia?

  • Sits atop the 4th ventricle



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Output from Cerebellum

  • Smoothes muscle contractions, maintains muscle tone & posture, coordinates motions of different joints, aids in learning motor skills & coordinates eye movements


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Midbrain

  • ____________________

  • Mes. aqueduct

  • CN III and IV

    • eye movement

  • Cerebral peduncles hold corticospinal tract

  • Tegmentum connects to cerebellum & helps control fine movements through red nucleus

  • Substantia nigra sends inhibitory signals to basal nuclei & thalamus


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Superior & Inferior Colliculus

  • Tectum (4 nuclei) called corpora quadrigemina

    • superior colliculus

    • inferior colliculus


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Reticular Formation

  • Clusters of gray matter scattered throughout pons, midbrain & medulla

  • Regulate balance & posture

    • relaying information from eyes & ears to cerebellum

    • gaze centers allow you to track moving object

  • Includes cardiac & vasomotor centers

  • Analgesic pathways

  • Regulates sleep, conscious attention, fatigue


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Thalamus

  • Oval mass of gray matter in center of ________________

  • Receives nearly all sensory information on its way to cerebral cortex

    • integrate & directs information to appropriate areas

  • Interconnected to limbic system so involved in emotional & memory functions


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Hypothalamus

  • Walls & floor of 3rd ventricle

  • Functions

    • hormone secretion & pituitary

    • autonomic NS control

    • thermoregulation

    • food & water intake

    • sleep & circadian rhythms

    • memory (mammillary bodies)

    • emotional behavior


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Epithalamus (Pineal Gland)

No output

In fish, amphibians, and reptiles monitors day and season length

Endocrine function in mammals, secreting melatonin

Seasonal sexual cycles

Humans - circadian


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Cerebrum -- Gross Anatomy

  • Cerebral cortex is 3mm layer of gray matter with extensive folds to increase surface area ---- divided into lobes


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Functions of Cerebrum Lobes

  • Frontal contains voluntary motor functions and areas for planning, mood, smell and social judgement

  • Parietal contains areas for sensory reception & integration of sensory information

  • Occipital is visual center of brain

  • Temporal contains areas for hearing, smell, learning, memory, emotional behavior


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Association Areas

Association areas interpret information

  • Somesthetic association area

    • limb position, location of touch or pain, and shape, weight & texture of an object

  • Visual association area

    • identify the things we see

  • Auditory association area

    • remember the name of music or identify a person by voice

  • Motor association area



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Basal Nuclei

  • Masses of gray matter deep to cerebral cortex

  • Receive input from substantia nigra & motor cortex & send signals back to these regions

  • Involved in motor control & inhibition of tremors


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LimbicSystem

  • Loop of cortical structures surrounding deep brain

    • amygdala, hippocampus, fornix & cingulate gyrus

  • Amydala important in ________________ and ____________________________ in memory


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Somesthetic Sensation

Somatosensory area is postcentral gyrus


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Sensory Homunculus

  • Demonstrates that the area of the cortex dedicated to the sensations of various body parts is proportional to how sensitive that part of the body is.

Ditto for Motor Homunculus


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Motor Control

  • Intention to contract a muscle begins in motor association (premotor) area of frontal lobes

  • Precentral gyrus (primary motor area) processes that order by sending signals to the spinal cord

    • upper motor neurons

    • to contralateral muscles

  • Motor homunculus is proportional to number of muscle motor units in a region


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