the brain

human anatomy and physiology lecture 7

provides protection to the brain

• cranial bones

• meninges

• blood-brain barrier

• cerebrospinal fluid

meninges

three connective tissue membranes that lie external to the central nervous system

functions of the meninges

• cover and protect the central nervous system

• protect blood vessels that enclose venous sinuses

• contain cerebrospinal fluid

• form partitions in the skull

blood-brain barrier

maintains a stable chemical environment for the brain

three mechanisms of the blood-brain barrier

• continuous endothelium of the capillary walls (tight junctions)

• thick basal lamina surrounding the capillaries

• astrocytes cling to the capillaries aiding in the formation of tight junctions

cerebrospinal fluid

filtrate of plasma that nourishes the brain

functions of cerebrospinal fluid

• mechanical protection: shock-absorbing medium, reduces weight of brain

• chemical protection: optimizes ionic environment for neuron signaling

• circulation: transports nutrients and chemical messengers, allows for removal of waste

ventricles

hallow chambers filled with cerebrospinal fluid, lined with ependymal cells

choroid plexus

forms cerebrospinal fluid by filtering blood plasma, helps cleanse the cerebrospinal fluid by removing wastes and unnecessary solutes, one in each ventricle

major structures of the brain

• cerebrum

• diencephalon

• brainstem

• cerebellum

cerebrum

conscious thought process, memory storage and processing, regulation of skeletal muscle contractions

components of the diencephalon

thalamus and hypothalamus

thalamus

relays and filters sensory information, mediate sensation, motor activities, learning, and memory

hypothalamus

controls emotions, autonomic functions, and hormone production, coordinating autonomic and endocrine control of homeostasis

components of the brainstem

medulla oblongata, cardiovascular and respiratory centers

brainstem

responsible for automatic behaviours required for survival, provides pathway for tracts running between higher and lower brain centers

medulla oblongata

relays information, autonomic center for regulation of visceral function

cerebellum

coordinates complex somatic motor movements, such as:

• adjusting postural muscles

• fine-tuning learned movements

• receives proprioceptive, visual, tactile, balance, and auditory sensations

• compares information from cerebrum with sensory feedback

four lobes of the cerebral hemispheres

• frontal lobe

• parietal lobe

• occipital lobe

• temporal lobe

cortex

superficial layer of gray matter

basal nuclei

islands of gray matter situated deep within the white matter

gyrus

raised edge

sulcus

superficial fold of grey matter

fissure

deep fold of grey matter

central sulcus

separates the frontal and parietal lobe

longitudinal fissure

separates the two sides of the cerebrum

corpus callosum

communicates between the left and right hemispheres of the cerebral cortex

motor areas controlling voluntary movement

• primary motor cortex

• premotor area

• Broca’s area

primary motor cortex

allow conscious control of precise and skilled voluntary movement, precentral gyrus

premotor area

controls learned motor skills that are repetitive in nature, acts as a memory bank for skilled movements, anterior to the primary motor area

Broca’s area

motor speech area that directs movement of muscles involved in speech production, only present in one hemisphere (usually left)

areas concerned with conscious sensation

• primary somatosensory cortex

• visual cortex

• auditory cortex

• olfactory cortex

• gustatory cortex

• vestibular cortex

primary somatosensory cortex

contralateral, receives afferent input from sensory receptors (touch, pressure, pain, vibration, temperature)

visual cortex

image perception, colour, shape, found in the occipital lobe

association areas

analyze sensory input to interpret incoming data, function to interpret and coordinate a motor response

four association areas

• somatosensory association cortex

• visual association area

• auditory association area

• somatic motor association area (premotor cortex)

somatosensory association cortex

acts to integrate the sensory input from the primary somatosensory cortex and produce an understanding of the object being felt

visual association area

allows for recognition and appreciation of visual stimuli

auditory association area

memories of sound are stored as a reference, individual word recognition but not language comprehension, sends feedback to the speech area

integrative areas

receive information from many association areas and direct extremely complex motor activities and participate in analytical functions

three integrative areas

• general interpretation area / common integrative area

• speech center

• prefrontal cortex

general interpretation area

receives input from all sensory association areas and integrates incoming signals into a single thought or understanding of the situation, found only in one hemisphere (usually left)

left hemisphere of speech area

language dominant

• forms speech, words analysis, language comprehension

• controls breathing for vocalization

right hemisphere of speech area

interpreting body language, tone, voice, and gestures

Wernicke’s area

language comprehension, integrates auditory and visual memories

prefrontal cortex

involved with intellect, complex learning, recall, event sequencing, and personality, develops slowly as we mature