BIO 240 Exam 2 Martha

Protection of the Brain

• Bony Cranium

• Connective Tissue

• Blood-Brain Barrier

Dura Mater

Tough, double layer of connective tissue that forms the outer meningeal membrane

Layers of Dura Mater

• Periosteal layer

• Meningeal layer

Periosteal layer (superficial)

Forms the periosteum on o internal surface of cranial bones

Meningeal layer (deep)

Innermost dura layer; sometimes referred to as the “true” dura mater

Dural Sinus

• space found between the periosteal and meningeal layers

• acts as modified vein, collecting venous blood and CSF

Dural Septa

occurs when two meningeal layers meet and extend inward, partitioning specific regions of the brain providing support and stabilization

Epidural Space

a potential space that contains arteries and veins that support the bones of the cranium and the meninges

Subdural Space

potential space found between the dura and arachnoid mater where fluid can collect

When do the epidural and subdural spaces become real spaces

Occurs when blood pools in these regions and compresses the brain tissues, or when spaces are filled with fluids and/or blood

Arachnoid Mater

connective tissue membrane located next to, and deep of, the subdural space

Subarachnoid space

filled with CSF which circulates throughout this space, ultimately moving through the arachnoid villil and into the dural sinuses where it is added to blood

Arachnoid trabeculae

membrane extensions composed of collagen and elastic fibers that transverse the subarachnoid space connecting the superficial arachnoid mater to the deeper pia mater

Arachnoid Villi

• CSF forms in the ventricles of the brain and drains into, and circulates through, the subarachnoid space of the meninges

• CSF movement is driven by a one-way pressure gradient (CSF pressure > than venous pressure)-

• CSF is routed from the subarachnoid space into arachnoid villi which transport it into the dural sinus where it mixes with venous bloo

Pia Mater

Innermost, thin meningeal layer that adheres to the contours of the brain surface

Fissure

deep, defined depresssion in the brain surface

Gyrus

elevated regions of the cerebral cortex

Sulcus

shallow groove in the cerebral cortex

Ventricles of the brain

• lateral ventricles (2)

• third ventricle

• fourth ventricle

CSF Fucntions

• buoyancy

• protection

• environmental stability

• supports nervous tissue

CSF is largely formed at the

Choroid plexus and ependymal cells

CSF circulation

lateral>interventricular foramen>third>cerebral aqueduct>fourth

CSF flows through the subarachnoid space through

the lateral and medial aperatures

Choroid Plexus

• forms a selective barrier that determines what materials move from the blood plasma into the ventricles, forming the CSF

• composed of capillaries, pia mater, and ependymal cells

CSF formations

• 30% from choroid plexus

• 30% from ependymal cells lining the ventricles

• 40% from fluids moving into the subarachnoid space

Substances that can cross Blood Brain Barrier

water, respiratory gases, glucose, lipid-soluble molecules, drugs, cocaine, meth, nicotine, caffeine, alcohol

Missing or reduced blood brain barrier locations

• choroid plexus

• hypothalamus

• pineal gland

Blood-Brain barrier

• highly selective semipermeable barrier that regulates which substances can, or can not, enter the brain’s interstitial fluid

• helps prevent neuron exposure to harmful substances such as drugs and waste products

• protects the brain from hormones and neurotransmitters fluctuations maintaining a constant environment for the brain

Blood-brain barrier composition

• Endothelial cells

• Astrocytes

  • Perivascular feet

Contralateral

the cerebral hemispheres receive sensory information, and send motor commands, to the opposite side of the body

Lateralization

all though functional overlap exists among the cerebral hemispheres, each hemisphere specializes in specific higher-order functions (speech)

Four Major Regions of the Human Brain

• Cerebrum

• Diencephalon

• Brainstem

• Cerebellum

Hemispheres of brain are connected by

corpus callosum

Gray matter

• cell bodies

• dendrites

• unmyelinated axons

White matter

• myelinated axons

Tracts

bundles of parallel axons in the CNS

Cerebral Nuclei

paired masses of gray matter located within the deeper central white matter

• primary function is to regulate motor output initiated by the cerebral cortex

  • helps inhibit unwanted movements

    • Parkinson and Huntington diseases impact this are resulting in jerky, involuntary movements

Association Tracts

bundles of axons that connect regions of cerebral cortex within same hemisphere

Longitudinal fasciculi

connects different lobes

Arcuate fibers

connect areas within the same lobe

Projection tracts

link the cerbreal cortex to inferior brain regions and spinal cord

Commissural tracts (in corpus callosum)

connect the right and left hemispheres

Frontal Lobe

primarily concerned with voluntary motor functions (including speech) and plays a major role in concentration, verbal communication, decision making, planning and personality

Primary Motor Cortex

controls volunatary skeletal muscle activity (contralateral)

Premotor cortex

coordinates learned, skilled motor activities

Frontal Eye Field

controls eye movement for reading & binocular vision

Motor Speech Area

controls muscular movements for vocalization (left hemisphere for most individuals)

Primary Motor Cortex (somatic motor area) located in

pre-central gyrus

Parietal Lobe

general sensory input related to touch and body position; conscious of sensations received

Primary somatosensory cortex

Receives somatic sensory information from receptors of the skin (touch, pressure, pain, temperature) and proprioceptors

conscious of these sensations

Somatosensory association area

integrates sensory information allowing us to identify objects by feel based on previous experiences

identify pressure, texture, temperature, shape

Primary Somatosensory Cortex is located in the

postcentral gyrus

Temporal Lobe

involved with hearing and smelling

Primary auditory cortex

receives and processes sound

Auditory association area

interprets sounds; stores and retrieves memories of sounds

Primary olfactory cortex

provides conscious awareness of smells

Occipital Lobe

receives, process and stores visual information

Primary visual cortex

Receives and processes incoming visual information

Visual association area

integrates color, movement and form to identify things we see based on memories

Insula

involved in memory and the interpretation of taste

Primary Gustatory cortex

involved in processing taste information

Categorical hemisphere (left for most)

• specialized for language abilities, functions in categorization and analysis

• contains Wernicke area and motor speech area

• Motor speech area (Broca area) controls the movement required for vocalization

• Wernicke area essential to the recognition, understanding, and comprehension of spoken or written language

• Left hemisphere of brain for most

Representational Hemisphere

• concerned with visuospatial relationships, imagination, comparison of senses

• Right hemisphere of the brain for most

Lateralization differs between sexes (sexual dimorphism)

• males suffer more functional loss when one hemisphere damaged

• females more likely to have bilateral (both hemispheres) language processing

• Women’s brains more coordinated between hemispheres compared to men with a thicker corpus callosum

Prefrontal Cortex

• located in frontal lobe- rostral to the premotor cortex

• retrieves and coordinates information from multiple areas of the brain

• involved in planning future behaviors, evaluating consequences

• this region continues to develop into 20’s

Select Cerebral Nuclei

• Caudate nucleus

• Lentiform nucleus

• Amygdaloid body

Caudate nucleus

helps produce pattern and rhythm of walking movements

Lentiform nucleus

composed of putamen and globus pallidus

Putamen

helps control movements at subconscious level

Globus Pallidus

influences thalamus to adjust muscle tone

Amygdaloid body

functions in mood, emotions

Diencephalon components

• thalamus

• hypothalamus

• epithalamus

Thalamus

contains right and left thalamic thalamic bodies each with multiple groups of nuclei, that are connected by the intermediate mass

Functions of Thalamus

• the thalamus is the final relay point for all incoming conscious sensory information except olfaction

• information is processed and selectively sent to the coordinating cerebral cortex region

  • acts as an information filter, relaying some signals to cortex but not others ( removes background noise)

Function of the Hypothalamus

• control of autonomic nervous system

• control of endocrine system

• regulation of body temperature

• emotional behavior

• food intake

• water intake

• sleep-wake rhythms

Functions fo Epithalamus

• pineal gland

  • endocrine gland that secretes melatoninc

  • helps regulate day-night cycles, circadian rhythm

• Habenular nuclei

  • involved in visceral and emotional responses to odors

Limbic System

The “emotional brain” composed of multiple cerebral and diencephalic structures that collectively process and experience emotions

Parts of the Limbic System

• Cingulate gyrus

• Fornix

• Hippocampus

• Amygdaloid body

• Olfactory tract

• Olfactory bulb

Cingulate gyrus

receives input from other components of limbic system

Hippocampus (and associated paraphippocampal gyrus)

• assists in storing/forming long-term memory

  • neurogenesis occurs here (adult stem cells)

  • fornix is white tract that connects the hippocampus to the other limbic structures

Amygdaloid body

• involved in several aspects of emotion especially fear

  • attaches emotions to memories

Olfactory structures (bulbs, tracts, and olfactory cortex)

process odors that can provoke emotions

Reticular Formation

• loosely organized gray matter of brain steam

  • contains both a motor and sensory component

Motor component of reticular formation

regulates muscle tone through its connection with the spinal cord and assists in autonomic functions

Sensory component of reticular formation (Reticular Activating system)

process sensory information determining what signals get sent to the cortex to bring about alertness/awareness (regulates levels of consciousness)

Components of Brainstem

• Midbrain

• Pons

• Medulla Oblongata

Components of Midbrain

• Cerebral peduncle

• Superior cerebellar peduncle

• Substantia Nigra

• Tectum

• Tegmentum

Cerebral Peduncle

motor tracts that relay voluntary motor commands from the primary motor cortex of each cerebral hemisphere

Superior cerebellar peduncle

tracts that connect the cerebellum and midbrain

Substantia Nigra

nuclei that house neurons that produce dopamine which is involved in the control of movement, emotional response, and the pleasure and pain response

Tectum

• sensory nuclei that control visual reflex and tracking (superior colliculi)

• controls auditory reflexes (inferior colliculi)

Tegmentum

• contains the red nuclei and reticular formation

• integrates information from cerebrum and cerebellum

• issues involuntary motor commands to help maintain posutre

Pons

• contains sensory and motor tracts connecting brain and spinal cord

• houses sensory and motor cranial nerve nuclei (trigeminal, abducens, and facial)

Components of Pons

• Middle cerebellar peduncle

• Pontine respiratory center

• Superior Olivary Nuclei

Middle cerebellar peduncle

contains axons that connect the pons and cerebellum

Pontine Respiratory center

contain autonomic nuclei that regulate smooth transitions between inspiration and expiration

works with medulla oblongata to regulate the skeletal muscles of breathing

Superior olivary nuclei

involved in multiple pathways for hearing including sound source localization

Medulla Oblongata

• continuous with the spinal cord

• contains sensory and motor tracts that connect the brain and spinal cord

• location of decussation of the pyramids

• inferior olivary nucleus

• inferior cerebellar peduncles

• nucleus cuneatus & nucleus gracilis

• contains cranial nerve nuclei ( vestibulocochlear, glossopharyngeal, vagus, accessory, and hypoglossal nerves

• Contains autonomic nuclei

  • cardiac vascular center

  • medullary respiratory center

  • other nuclei for varied functions

Cerebellum

doesn’t initiate skeletal muscle movement but coordinates and “fine-tunes movements while helping maintain equilibrium and posture

• continuously receives motor plans and sensory feedback

• helps maintain equilibrium and posture

vermis

Hemispheres of cerebellum are connected by the