PROGRESS TEST 2! Flashcards
THE CENTRAL NERVOUS SYSTEM (CNS) CONSISTS OF:
BRAIN (neurons & glia) + SPINAL CORD (neuron & glia)
PERIPHERAL NERVOUS SYSTEM (PNS) CONSISTS OF:
PERIPHERAL NERVES & GANGLIA (neurons & glia)
NEURONS (NERVE CELLS)
- CELLS SPECIALISED FOR TRANSMISSION OF INFO
- FOUR MORPHOLOGICAL TYPES
- STRUCTURAL COMPONENT ( DENDRITES > CELL BODY > AXON > AXON TERMINALS)
ROLE OF DENDRITES:
- RECIEVE INPUT
- SEND INFORMATION TO THE CELL BODY
ROLE OF THE CELL BODY:
- CONTAINS NUCLEUS & ORGANELLE
- SUMS THE INPUT
ROLE OF AXON:
- CARRIES ELECTRICAL IMPULSES
- MAY OR MAY NOT BE MYELINATED
AXON TERMINALS:
- END OF THE AXON
- NEUROTRANSMITTER RELEASE
GLIA:
- SUPPORT FOR NEURONS
- FIVE BASIC TYPES a) 4 IN CNS b) 1 IN THE PNS
- EACH TYPE HAS A SPECIFIC FUNCTION.
IN THE CNS:
- A GROUP OF CELL BODIES = ?
- A BUNDLE OF AXON = ?
- GROUP OF CELL BODIES IN CEREBRAL CORTEX = ?
- BUNDLE OF AXONS IN CEREBRAL CORTEX = ?
- = NUCLEUS
- = TRACT
- = GREY MATTER
- = WHITE MATTER
IN THE PNS:
- A GROUP OF CELL BODIES = ?
- BUNDLE OF ZONS = ?
- = GANGLION
2. = NERVE
INPUT ZONE:
DENDRITES & CELL BODY
- RECEIVES CHEMICAL SIGNALS FROM OTHER NEURONS
SUMATION ZONE:
AXON HILLOCK
- SUMMATION OF INPUTS
CONDUCTION ZONE:
AXON, MAY BE QUIET LONG
- CARRY ELECTRICAL SIGNALS BETWEEN BRAIN AREAS, TO & FROM SPINAL CORD OR FROM PERIPHERAL SENSORY RECEPTORS AND TO EFFECTOR CELLS.
OUTPUT ZONE:
AXON TERMINALS
- CONTACT WITH INPUT ZONE OF OTHER NEURONS OR EFFECTORS
- RELEASE OF NEUROTRANSMITTER.
4 MORPHOLOGICAL TYPES OF NEURONS
- MULTIPOLAR (multiple processes emanate from the cell body)
- BIPOLAR (two processes emanate from the cell body)
- UNIPOLAR (one process emanates from the cell body - then branches into dendrite & axon)
- ANOXIC (axones - no distinct axon & all processes look alike)
TYPES OF GLIAL CELLS FOUND IN THE CNS
- ASTROCYTES - supply nutrients to neurons - ensheath blood capillaries (injury response)
- MICROGLIA - immune cells of the CNS - engulf micro-organisms & debris
- EPENDYMAL CELLS - line fluid-filled spaces of brain & spinal cord. - have cilia to circulate CSF
- OLIGODENDROCYTES - support nerve fibres - ensheath them with myelin
GLIAL CELL FOUND IN THE PNS
SCHWANN CELLS - support peripheral nerve fibres & ensheath them with myelin.
- similar to the oligodendrocytes of the CNS.
MYELIN SHEATH - BASIC STRUCTURE:
MULTIPLE SCHWANN CELLS IN A LINE.
NODES OF RAINIVER = GAPS BETWEEN MYELIN - THESE INCREASE CONDUCTION VELOCITY
WHAT IS A SYNAPSE?
A JUNCTION THAT HELPS WITH COMMUNICATION BETWEEN NEURONS
WHAT IS AFFERENT INFORMATION
INFORMATION THAT GOES INTO THE BRAIN (ASCENDING)
WHAT IS EFFERENT INFORMATION?
RESPONSE THAT COMES OUT OF THE BRAIN (DESCENDING)
WHAT IS SOMATIC INFORMATION:
THE STUFF WE ARE AWARE OF, AND HAVE CONTROL OVER
- VOLUNTARY MUSCLE CONTROL (SOMATIC EFFERENT - MOTOR)
- SENSORY INFORMATION THAT WE’RE AWARE OF (SOMATIC AFFERENT - SENSORY)
WHAT IS AUTONOMIC INFORMATION:
THE STUDD WE’RE NOT AWARE OF, HAVE NO CONTROL OVER.
- INVOLUNTARY MUSCLE CONTROL (AUTONOMIC EFFERENT - MOTOR)
- SENSORY INFO THAT WE DON’T KNOW ABOUT (AUTONOMIC AFFERENT - SENSORY)
SOMATIC EFFERENT DIVISION - THE TWO NEURONS BETWEEN BRAIN & EFFECTOR:
- UPPER MOTOR NEURON
2. LOWER MOTOR NEURON
UPPER MOTOR NEURON..?
CELL BODY IN BRAIN.
AXON IN SPINAL CORD
AXON IS MYELINATED
LOWER MOTOR NEURON..?
CELL BODY IN SPINAL CORD
AXON IN SPINAL NERVE
AXON IS MYELINATED
NEUROTRANSMITTER AT THE SYNAPTIC CLEFT?
ACETYLCHOLINE (Ach)
SOMATIC EFFERENT DIVISION SUMMARY:
- VOLUNTARY MOVEMENT
- 2 NEURONS BETWEEN BRAIN & EFFECTOR (UPPER & LOWER MOTOR NEURON)
- AXONS ARE MYELINATED
- NEUROTRANSMITTER = ACETYLCHOLINE (Ach)
- EFFECTOR = SKELETAL MUSCLE
AUTONOMIC EFFERENT NERVOUS SYSTEM:
- INVOLUNTARY CONTROL
- TWO DIVISIONS - SYMPATHETIC & PARASYMPATHETIC
- EFFECTORS = SMOOTH MUSCLE, CARDIAC MUSCLE, GLANDS & ADIPOSE (FAT) TISSUE
- 3 NEURONS BETWEEN BRAIN & EFFECTOR
NEURON #1:
- CELL BODY IN VRAIN
- AXON IN BRAIN OR SPINAL CORD (CNS)
NEURON #2
- CELL BODY IN BRAIN/SPINAL CORD
- AXON EXTENDS IN PNS
- MYELINATED
- SYNAPSE IN AUTONOMIC GANGLION
- PRE-GANGLIONIC NEURON
- NEUROTRANSMITTER = ACETYLCHOLINE (Ach)
NEURON #3
- CELL BODY IN PNS, AUTONOMIC GANGLION
- AXON EXTENDS ON PNS, TO EFFECTOR ORGAN
- UNMYLENATED
- SYNAPSE ON EFFECTOR ORGAN
- POST-GANGLIONIC NEURON
- NEUROTRANSMITTER = ACETYLCHOLINE (Ach) OR NOREPINEPHERON
SYMPATHETIC NERVOUS SYSTEM: NOREPINEPHERON & Ach
- PREPARES BODY FOR ACUTE/STRESS RESPONSES
> ‘FIGHT OR FLIGHT’ SYSTEM - EFFECTS INCLUDE: - INCREASED; HEART RATE, BLOOD FLOW TO MUSCLES, GASTRIC MOBILITY
- CONSTRICTING BLOOD VESSELS TO SKIN & VISCERA
PARASYMPATHETIC NERVOUS SYSTEM: Ach
- PREPARES BODY FOR RESTFUL SITUATIONS.
> ‘REST AND DIGEST’ SYSTEM - EFFECTS INCLUDE: - DECREASE IN; HEART RATE, GASTRIC MOTILITY, PUPIL SIZE, SALVATION
SYMPATHETIC NERVOUS SYSTEM - PRE-GANGLIONIC NEURON:
- CELL BODY IN THORACOLUMBAR LEVELS OF SPINAL CORD (CNS)
- AXON IS SHORT
- AXON TERMINALS AND SYNAPSE IN SYMPATHETIC GANGLION
SYMPATHETIC NERVOUS SYSTEM - POST-GANGLIONIC NEURON:
- CELL BODY IN SYMPATHETIC GANGLION - SYMPATHETIC CHAIN GANGLIA
- AXON IS LONG
SYMPATHETIC CHAIN GANGLIA:
- FOUND ON EITHER SIDE OF THE VERTEBRAL COLUMN
- 21 - 23 PAIRS
- THIS IS THE PLACE WHERE PRE-GANGLIONIC (NEURON #2) AXONS SYNAPSE
> ONTO POST GANGLIONIC (NEURON #3) INPUT ZONE.
PARASYMPATHETIC NERVOUS SYSTEM - PRE-GANGLIONIC NEURON:
- CELL BODIES IN CRANIAL (BRAINSTEM) AND SACRAL (SPINAL CORD) LEVELS
- AXON IS LONG
- AXON TERMINALS & SYNAPSE IN PARASYMPATHETIC GANGLIA (IN OR NEAR EFFECTORS)
PARASYMPATHETIC NERVOUS SYSTEM - POST-GANGLIONIC NEURON:
- CELL BODY IN PARASYMPATHETIC GANGLIA IN OR NEAR THE EFFECTOR ORGANS
- AXON IS HSORT
ACTION POTENTIAL:
- REVERSAL OF TRANS-MEMBRANE VOLTAGE THAT IS COMPLETED IN 2-3 MS
- INFORMATION IS ENCODED AND TRANSMITTED VIA ELECTRICAL AND CHEMICAL SIGNALLING.
RESTING MEMBRANE POTENTIAL:
THE ESTABLISHMENT & MAINTENANCE OF A RESTING MEMBRANE POTENTIAL IS AN ESSENTIAL FOUNDATION FOR ELECTRICAL SIGNALLING.
> AT REST, THE INTERCELLULAR SPACE HAS MORE NEGATIVE CHARGE THAN TH EXTRACELLULAR SPACE, CREATING AN ‘ELECTRICAL GRADIENT’ = RESTING MEMBRANE POTENTIAL
ION CHANNELS:
- THESE ARE THE REGULATORS OF CHANGES IN MEMBRANE PERMEABILITY
- PERMIT SELECTIVE PASSAGE OF IONS INTO & OUT OF THE CELL.
- CAUSED DUE TO THE OPEN OR CLOSED STATE OF SPECIFIC ION CHANNELS (GATING)
- RESULTS IN CURRENT FLOW AND CHANGE IN TRANSMEMBRANE VOLTAGE.
CHEMICALLY GATED ION CHANNELS:
- OPEN AND CLOSE IN RESPONSE TO CHEMICALS
- Ach BINDS TO IT’S BINDING SITE - OPENS THE ION CHANNEL ALLOWING Na (e.g.) THROUGH
- CHEMICALLY GATED ION CHANNELS OPEN WHEN THEY BIND SPECIFIC CHEMICALS
> FOUND MOSTLY ON THE DENDRITES & CELL BODY OF A NEURON. - AREAS WHERE MOST SYNAPTIC COMMUNICATIONS OCCUR.
VOLTAGE GATED ION CHANNELS:
- ACTIVATED BY CHANGES IN THE ELECTRICAL MEMBRANE NEAR THE CHANNEL.
- MEMBRANE POTENTIAL ALTERS THE CONFORMATION OF THE CHANNEL PROTEINS
> THIS REGULATES THE OPENING & CLOSING.
MECHANICALLY GATED ION CHANNELS:
- OPEN IN RESPONSE TO MECHANICAL STIMULI - PHYSICALLY DISTORTS THE NEURONS MEMBRANE SURFACE
- CONVERTS MECHANICAL STIMULI INTO ELECTRICAL SIGNAL.
- OPENS DUE TO APPLIED PRESSURE
WHERE ARE CHEMICALLY GATED ION CHANNELS FOUND?
DENDRITES & CELL BODY OF THE NEURON
WHERE ARE VOLTAGE GATED Na+ AND K+ CHANNELS FOUND?
AXON OF THE NEURON - ALONG THE AXON .
> (depends on myelinated or un-myelinated)
WHERE ARE VOLTAGE GATED Ca2+ CHANNELS FOUND?
FOUND N AXON TERMINALS.
LOCAL POTENTIALS
THE RESULT OF OPENING ION CHANNELS IN A REIGON OF RECEIPT OF CHEMICAL SIGNALS.
- CHANGES IN THE MEMBRANE POTENTIAL THAT CANNOT SPREAD FAR FROM THE SITE OF STIMULATION.
DEPOLARIZATION=?
ANY SHIFT FROM THE RESTING MEMBRANE POTENTIAL TOWARDS A MORE POSITIVE VALUE.
- ALSO APPLIES TO CHANGES IN POTENTIAL FROM -70mV TO SMALLER NEGATIVE VALUES (TOWARDS 0mV) AS WELL AS TO MEMBRANE POTENTIALS ABOVE 0mV
- AS PLASMA MEMBRANE DEPOLARISES, EXTRACELLULAR SODIUM IONS MOVE TOWARDS THE OPEN CHANNELS REPLACING IONS THAT HAVE ENTERED THE CELL.
WHAT IS A LOCAL CURRENT?
THE MOVEMENT OF POSITIVE CHARGES PARALLEL TO THE INNER & OUTTER SURFACES OF THE MEMBRANE.
REPOLARIZATION=?
CHEMICAL STIMULUS IS REMOVED, AND THE MEMBRANE RETURNS TO ITS NORMAL RESTING MEMBRANE POTENTIAL AS THE EXCESS SODIUM IONS ARE TRANSPORTED OUT OF THE CYTOSOL.
HYPERPOLARIZATION=?
- SHIFT IN THE MEMBRANE POTENTIAL PAST (BELOW) RESTING LEVEL.
TWO WAYS THE EFFECTS OF LOCAL POTENTIALS CAN BE SUMMED:
- TIME - TEMPORAL SUMMATION
2. SPACE - SPATIAL SUMMATION
THE AXON HILLOCK / THE INITIAL SEGMENT:
POINT WHERE THE AXON JOINS THE NEURON CELL BODY
- HIGH DENSITY OF VOLTAGE GATED Na CHANNELS
- WHERE ACTION POTENTIALS ARE GENERATED
ACTION POTENTIAL - THRESHOLD
- DEPOLARISING LOCAL POTENTIALS MAY RESULT IN OPENING OF VOLTAE GATED Na CHANNELS
- THIS DRIVES FURTHER DEPOLARISATION
- DEPOLARISATION THEN REACHES A POINT AT WHICH LARGE NUMBERS OF CHANNELS OPEN RESULTS IN A SUDDEN LARGE INCREASE IN Na INFLUX = THRESHOLD REACHED
THRESHOLD POTENTIAL =?
THE MINIMUM POTENTIAL NEEDED IN
ORDER FOR VOLTAGE-GATED CHANNELS TO OPEN
> THESE ARE THE KEY CHANNELS CAUSING THE PROPAGATION OF ACTION POTENTIALS.
WHAT IS INITIAL DEPOLARISATION?
LOCAL POTENTIALS CAUSE LOCAL DEPOLARISATION FROM SODIUM INFLUX THROUGH LIGAND/CHEMICAL GATED CHANNELS.
WHAT IS RAPID DEPOLARISATION?
LOCAL DEPOLARISATION CAUSES THRESHOLD TO BE REACHED, AND VOLTAGE GATED SODIUM CHANNELS OPEN CAUSING RAPID DEPOLARISATION TO SPREAD DOWN THE AXON IN A ‘MEXICAN WAVE’ FASHION.
WHAT IS REPOLARIZATION?
SODIUM CHANNELS CLOSE AT MAXIMUM DEPOLARISATION (+30mV) VOLTAGE GATED K+ CHANNELS OPEN WHICH LET OUT K+, REPOLARIZING THE CELL.
WHAT IS HYPERPOLARIZATION?
POTASSIUM CHANNELS OVERSHOOT AND THE MEMBRANE POTENTIALS BECOME MORE NEGATIVE THAN THE RESTING MEMBRANE POTENTIAL
WHAT IS THE RESTING MEMBRANE POTENTIAL?
RESTORED BY THE SODIUM/POTASSIUM AtPase TO AROUND -70mV
WHAT IS THE ABSOLUTE REFECTORY PERIOD?
THIS IS THE PERIOD WHERE IT IS IMPOSSIBLE TO SEND ANOTHER ACTION POTENTIAL.
THE INACTIVATION GATES OF THE SODIUM CHANNELS LOCK SHUT FOR A TIME AFTER THEY’RE OPENED - SO NO SODIUM WILL PASS THROUGH.
NO SODIUM = NO DEPOLARISATION = NO ACTION POTENTIALS
WHAT IS THE RELATIVE REFRACTORY PERIOD?
THIS IS THE PERIOD WHERE IT IS REALLY HARD TO SEND AN ACTION POTENTIAL.
- PERIOD OF TIME AFTER THE ABSOLUTE REFRACTORY PERIOD WHEN THE INACTIVATION GATES ARE OPEN AGAIN. HOWEVER THE CELL IS STILL HYPERPOLARIZED AFTER SENDING AN ACTION POTENTIAL - SO IT WILL TAKE EVEN MORE POSITIVE IONS THAN USUAL TO REACH THRESHOLD POTENTIAL.
BIG GRADED POTENTIAL NEEDED FOR ACTION POTENTIAL TO BE GENERATED.
WHAT ARE THE 3 WAYS TO INCREASE THE SPEED OF CONDUCTION?
- SIZE - BIGGER DIAMETER = FASTER
- SHEATH - MYELINATED = FASTER (INSULATION PREVENTS LOSS OF IONS
- SALTATORY CONDUCTION - NODES OF RANIVER (BETWEEN MYELIN) ALLOWS THE ACTION POTENTIAL TO ‘JUMP’ FROM NODE TO NODE DOWN THE NERVE.
WHAT IS A SYNAPSE?
JUNCTIONS BETWEEN EXCITABLE CELLS
SYNAPTIC TRANSMISSION #1
VOLTAGE CHANGE OF THE ACTION POTENTIAL IS TO OPEN THE VOLTAGE-GATED CALCIUM CHANNELS & ALLOW CALCIUM ENTRY.
SYNAPTIC TRANSIMISSION #2
CALCIUM CHANNELS OPEN, CALCIUM ENTER DOWN IT’S CALCIUM GRADIENT. SYNAPTIC VESICLES FUES & CONTENTS ARE DISCHARGED.
- CHEMICALLY-GATED ION CHANNEL OPENED ALLOWS THE ENTRY OF SODIUM BRINING POSITIVE CHARGE CAUSING DEPOLARISATION AT THIS SITE.
- IF BIG ENOUGH THIS COULD CAUSE THE OPENING OF VOLTAGE GATED SENSORS.
- THEREFOR INCREASING THE LIKELIHOOD THAT THE POST-SYNAPTIC CELL WILL FIRE AN ACTION POTENTIAL.
WHAT ARE MENINGES?
PROTECTIVE COVERING FOR THE BRAIN.
> THEY SIT BETWEEN THE CRANIUM & THE SURFACE OF THE BRAIN.
WHAT ARE THE 3 LAYERS OF PROTECTIVE TISSUE ASSOCIATED WITH TH MENINGES?
- DURA MATER = BENEATH THE BONE OF THE CRANIUM.
- ARACHNOID = BENEATH THE DURA MATER
- PIA MATER = GOES INTO THE INDENTATION OF THE SURFACE OF THE BRAIN
WHAT ARE THE 5 FEATURES OF THE DURA MATER?
- OUTER-MOST LAYER OF THE MENINGES
- DENSE & FIBROUS = TOUGH
- PRESENT IN 2 LAYERS (OUTER & INNER)
- SPACE BETWEEN THE LAYERS FORMS VENOUS SINUSES
- INNER LAYER FORMS DURA FOLDS.
DURA FOLDS ARE:
FORMED FROM THE INNER LAYER OF THE DURA MATER
THEY SEPERATE MAJOR DIVISIONS OF THE BRAIN
PROVIDES STABILITY OF THE BRAIN WITHIN THE CRANIUM
WHAT ARE THE 3 TYPES OF DURA FOLDS?
- FALX CEREBRI = SEPERATES CEREBRAL HEMISPHERES (MEDIAN PLANE)
- FALX CEREBELLI = SEPRATES CEREBELLAR HEMISPHERES (MEDIAN PLANE)
- TANTRUM CEREBELLA = SEPERATE THE CEREBRUM FROM THE CEREBELLUM
3 FEATURES OF VENOUS SINUS’:
- LOCATED WHERE THE TWO LAYERS OF THE DURA MATER SEPERATE
- COLLECTING VEINS (SPACE THAT COLLECTS LIQUID)
- COLLECT TWO THINGS;
1. VENOUS BLOOD FROM THE BRAIN
2. OLD CEREBROSPINAL FLUID AFTER IT HAS CYCLED THROUGH THE VENTRICULAR SYSTEM.
