Lecture 21 Flashcards
Blood/Brain barrier
Highly selective, semi-permeable membrane, maintained by astrocytes surrounding endothelium. Have special tight junctions that don’t allow cell transfer as easily; Easily impaired by inflammation.
What does it mean in T-cells are found in CSF?
Infection + Blocking pathogens/toxins
What diseases are caused by a damaged blood/brain barrier
Alzheimer’s, ALS, Epilepsy, stroke
Central nervous system
Brain, (cerebrum, brain stem, cerebellum) and spinal cord – protected by skull (cranium). Meninges - surround membranes of CNS
4 Layers surrounding the brain
Dura (firm fibrous – outer covering/ protective)
Arachnoid (middle - cushioning)
Sub Arachnoid (Contains CSF)
Pia (thin – inner) covers brain, spinal cord
PNS – peripheral nervous system
Nerves that branch off spinal cord, Somatic – voluntary movement, Autonomic (involuntary) (Sympathetic/Parasympathetic)
Autonomic (involuntary) NS
Controls smooth muscles, glands and organ functions
Sympathetic – “fight or flight”
Parasympathetic – “rest and digest”
Neurons
Nerve cells, transmit nerve impulses
Neurons
Nerve cells, transmit nerve impulses
Central body
Dendrites (transmit toward cell body) and axon (transmit away) emerge from it to transmit impulses
Neuroglia
Supporting cells - more numerous than neurons
Astrocytes
Long, star-shaped cells, numerous, highly branched process that provide structure/support and nourishment to neurons
Oligodendrocytes
Small cells, scanty cytoplasm, surround nerve cell axons: Schwann (PNS), Oligodendrocytes (CNS)
Microglia
Phagocytic cells – immune protection (Macrophages of NS)
Neuron signaling
Electric impulse carried - (250mph travel speed) activation by ion/chemical signals processed by dendrites and travel through Myelin sheath/nodes of Ranvier to send a message to another neuron or target cell
Depolarization
Activation by electrical impulse or chemical receptors send electrical signal down axon
Neurotransmitters
Glutamate (stimulatory) , dopamine (motivation), acetylcholine(neuromuscular), serotonin (mood) GABA (usually inhibitory), Adrenergic (norepinephrine/epinepherine)
Physical and mental health disorders associated with neurotransmitters
Schizophrenia, Mood disorders, Depression/Anxiety, PTSD, Parkinson’s, Migraines, Seizures, Addiction, Alzheimer’s, Insomnia.
What is the function of the brain and what is it composed of?
Control all bodily functions/organs (expect reflexes). It is composed of Neurons (nerve cells) and neuroglia (supporting cells) together = neuropil
Grey matter
More external (neuronal cell bodies, astrocytes and microglia)
White matter
Central distribution (axons and oligodendrocytes)
Afferent nerves (sensory)
Transmits impulses to the nervous system
Efferent nerves (motor)
Transmits impulses from brain or spinal cord to muscle
How are signals of a nerve impulse transmitted?
Neurotransmitters (Acetylcholine, norepinephrine, dopamine) occur in synapses where they are released at axon terminals and received by dendrites
Cerebral Cortex
Receives sensory input and initiates voluntary motor responses
Brain Stem
Involved in control of vital functions not under voluntary control (cardiac/respiratory regulation and function) and connects cortex to cerebellum
Cerebellum
Regulates balance, muscle tone, coordination (fine motor control)
Spinal cord
continuation of brain stem that conducts signals to body, also contains sensory and motor reflex neurons that are not under cortical control.
What are the 4 cavities in the brain called?
Ventricles (filled with CSF, responsible for the production (choroid plexus in each ventricle) and flow of CSF (neutral buoyancy))
Arterial blood supply
Large vessels enter base of skull. Vessels join to form arterial circle at base of brain (circle of Willis)
Venous blood
Returned from the brain into large venous sinuses in dura which drain into jugular veins
Closed system
Increased in volume, inflammation or intruding mass (blood/tumor) will put pressure on to the brain causing injury and death
Voluntary Motor Activity
Controlled by nerve impulses originating in upper motor neurons of the cerebral cortex (cortical neurons)
Pyramidal system
Controls voluntary motor functions
Extrapyramidal system
Regulates muscle groups concerned with coordinated motor functions (balance, coordination, reflexes)
Muscle tone
Passive firmness of muscle contraction and resistance to passive stretching (postural muscles) that is controlled by reflex arcs
Paralysis
Muscle no longer subject to voluntary control
Flaccid paralysis (PNS damage)
Destruction of lower (peripheral) motor neurons by disease (poliomyelitis) causing low muscle tone - atrophy
Spastic paralysis (CNS damage)
Disease or Injury to cortical neurons (stroke) causing increased muscle tone
Nervous system development
In embryonic development, CNS derives from the ectoderm and first appears as a thickened band of cells (neural plate). Neural folds are formed and fuse to form the neural tube (wk4) which is filled with CSF
What do the cerebral hemispheres develop?
The forebrain
The cerebellum and medulla form what?
The hindbrain
What are the 2 most common neural tube defects?
Spina bifida and Anencephaly
Anencephaly
Upper part (cephalic end) of neural tube fails to close and exposed brain tissue degenerates to mass of vascular connective tissue mixed with degenerated nervous tissue; Incompatible with life