chapter 14 Flashcards
where is the majority of the body’s neural tissue?
in the brain (97%)
how much does the brain weigh?
1.4 kg (3 lbs)
what is the typical brain volume?
750 ml to 2100 ml
what are the six regions of the brain?
cerebrum, cerebellum, diencephalon, midbrain, pons and medulla oblongata
where in the brain is conscious thought and intelligence produced?
neural cortex
cerebrum
- largest portion of the brain
- origination of conscious thoughts, sensations, memory, complex movements
- made of two cerebral hemispheres
cerebellum
- 2nd largest part of the brain
- adjusts ongoing movements
- coordinates repetitive body movements
- covered by cerebellar cortex
- coordinates skeletal muscle contractions
- maintains muscle tone and posture
diencephalon
- made of thalamus (3 divisions)
- links the cerebrum with the brain stem
thalamus
relays and processes sensory information
hypothalamus
floor of diencephalon
- controls hormone production, emotions and autonomic function
what connects the hypothalamus to the pituitary gland?
the infundibulum
pituitary gland
major endocrine gland that integrates nervous and endocrine systems
what does the brainstem do?
processes information between the spinal cord and cerebrum or cerebellum
what does the brainstem consist of?
the brainstem is made up of the midbrain, pons and medulla oblongata
midbrain
aka mesencephalon
- processes visual and auditory information/reflexes
- maintains consciousness
- controls reflex responses
pons
connects the cerebellum to the brain stem
- houses tracts involved in somatic and visceral motor control
medulla oblongata
connects the brain to the spinal cord
- relays information
- regulates autonomic functions (HR, BP, vasoconstriction, digestion)
- contains portions of motor and sensory tracts
reticular formation
regulates muscle tone
alerts cortex to incoming signal
maintains consciousness
what is the brain protected by?
cranium bones, cranial meninges and CSF
and BBB
dura mater
consists of outer and inner fibrous layers
- meningeal and periosteal layer
- venous sinuses between two layers
arachnoid mater
covers the brain, comes in contact with the dura mater
weblike, avascular
pia mater
attached to the brain by astrocytes
dural folds
inward folds in the meningeal dura mater
provide stabilization for the brain
contain dural sinuses (collecting veins)
what are the three dural folds?
falx cerebri
tentorium cerebelli
falx cerebelli
falx cerebri
- projects between cerebral hemispheres
- contains superior and inferior sagittal sinuses (venous sinuses)
tentorium cerebelli
- separates cerebellum and cerebrum
- transverse sinus which runs across the occipital bone to drain blood from the back of the head
falx cerebelli
divides the cerebellar hemispheres into two
cerebrospinal fluid
- surrounds the CNS
- cushions delicate neural structures
- supports the brain
- transports nutrients, chemical messengers and waste
what is a choroid plexus?
area within each brain ventricle that produces CSF
- made of special ependymal cells
- produces about 500 mL of CSF a day
CSF circulation route
choroid plexus - ventricles- central canal- subarachnoid space through apetures
a problem with CSF resorption in infants can cause what?
hydrocephaly
cranial trauma
head injury resulting from impact with another object
what absorbs CSF into venous circulation?
arachnoid granulations
how does arterial blood reach the brain?
though internal carotid arteries and vertebral arteries
how does venous blood leave the brain?
through internal jugular veins in the dural sinuses
importance of blood flow to the brain
- uses about 20% of body’s oxygen supply
- lack of oxygen can result in weakening or permanent damage of brain cells
glucose deficiency may produce
mental confusion, dizziness and unconsciousness
cerebrovascular disease
cardiovascular disorders that interfere with blood circulation to the brain
CVA
aka a stroke is when blood supply to a part of the brain is shut off
neurons will die
how is nervous tissue in the CNS isolated?
by the BBB
What forms the BBB?
capillary endothelial cells interconnected by tight junctions
what kind of compounds can cross the BBB?
- lipid soluble
- CO2, O2, ammonia, steroids, prostaglandins
what do astrocytes do for the BBB?
release chemicals that control endothelium permeability (nutrients, ions)
blood CSF barrier
- made of specialized ependymal cells that surround the choroid plexus capillaries
- limit compound movement into the CNS
- allow chemical comp. of blood and CSF to differ
where won’t you find the BBB?
- parts of the hypothalamus
- posterior lobe of pituitary gland (secretes ADH and oxytocin)
- pineal gland
- choroid plexus because ependymal cells maintain the blood CSF barrier
