Nervous system Flashcards
What are the two sections in the nervous system ?
central nervous system (brain and spinal cord) and peripheral nervous system (motor and sensory)
What are the main words used to describe positions within the brain?
Rostial ( towards head)// cordal (towards bum)// dorsal (back )// ventricle (belly)
What are the three section planes of the brain?
Horizontal (up and down) / coronal(front and back) / sagittal (left and right)
What are the categories can be used to classify neurons ?
number of neurons/ dendritic tree structure / axon length / neurotransmitter/ connection
What are meninges and their function?
= membranes
- main function is to protect the CNS
- there are 3 membranes including dura mater (toough outer layer / skull cap) // arachnoid - spinal web layer under dura // pia mater - thin inner layer located close to the CNS
What are some of the main components of the brain?
Cerebrum // Brain stem // Mid brain// hind brain (pons / medulla oblongata / cerebellum)
What are the 4 partitioning sections of the brain?
central sulcus// lateral sulcus // parieto- occupatial sulucus // calcarine sulcus
What is the difference between grey and white matter?
Grey = cell bodies // white = myelinated axons
*both apart of the spinal cord
What components are required to establish a potentail difference across a cell membrane ?
membrane permeability // ion gates and channels // movement of Sodium ions (moving inside the cell ) Potassium moving outside the cell / Proteins account for a small negative charge
What is the importance of potential difference for neuron and nervous function?
it allows neurons to generate electrical signals that transmit needed for synaptic transmission // network communication and all sensory systems
What are the three things ion flow is driven by?
concentration gradient // electrochemical gradient// energy driven pumps
What is the usual resting potential value of a membrane?
-70mv
What is some characteristics of a graded potential?
SHORT DISTANCE SIGNAL // always occurs in active areas of membrane
1. channel is closed // 2. signal causes Na+ channel to open and Na+ to flood in// 3. Na+ depolarises the local area// 4. channel closes // 5. Na+ moves into surrounding areas following electrochemical gradient due to closed channel this dies off quickly
How can potential difference be found?
An electrode can be placed inside the cell wall and voltage can then be compared between this and another electrode in the bath (representing outside the cell)
What are some properties of membranes?
hydrophobic phosphate heads // hydrophilic lipid tails// constant movement of the phospholipids makes the membrane ‘fluid’ // cholesterol molecules // transport and channel proteins// carbohydrate chain // glycolipids
How is an action potential generated?
a long distance signal // 1. At rest inside the cell is more negative // 2. Voltage sensitive Na+ channel then open, Na+ moves into the cell creating depolarisation (-55mV) // 3. Na+ channel opens further flooding more Na+ into the cell via the electrochemical gradient // 4. As NA+ channels are located adjacently, the opening of one has a knock on effect opening the others next to it// 5. Large depolarisation is created in the cell area near these ion channel (rising phase) // 5. Voltage graded potassium channels open , pumping K+ out of the cell (falling phase)// 6. Membrane potential is now more positive - positive ions are driven out of the cell creating repolarisation
How is an action potential propagated ?
VIA SALTATORY CONDUCTION-> nerve impulse ‘jumps’ between nodes of Ranvier due to myelination of nerve , causing the impulse to move faster through an axon (50 X faster than continuous conduction) // Naturally it is the wave of depolarisation and the sodium and potassium channels trying to maintain a state of equilibrium which drives the propagation of an action potential along an axon.// *Voltage-gated Na+ and K+ channels are located in nodes of Ranvier
What is synaptic transmission. Name the two types.
Transfer of information from one nerve to the next// ELECTRICAL - neurones are connected via gap junctions// CHEMICAL - junction between axon terminal of a neurone and the dendrites or cell body of another
What are the individual components required to establish a potential difference across a cell membrane?
sodium channel/ potassium channel// electrochemical gradient/ concentration gradient / polar and charged ions
What creates the resting potentail?
concentration and electrochemical gradient // positioning of sodium ions (more outside the cell) potassium ions(more inside the cell) and proteins (negative charge within the cell)// free flowing movement of the ions through channels within the membrane - using no ATP
What uses a resting membrane potentail?
Synaptic transmission / network communication// all sensory systems.
What are the two main simple steps which occur when a neurone is stimulated?
- neurotransmitter is released by an adjacent neurone // 2. sodium ion channel opens generating a nerve impulse
What is a graded potential? How is it generated?
A short-distance signal// 1. Neurotransmitter binds to a receptor site on a Na+ channel opening it// 2. Na+ flows into the cell depolarising the local area // 3. Na+ channel closes // 4. Na+ moves into surrounding area following an electrochemical gradient, as the channel shuts (step 3) this is a gradual process affecting a small area.
What is summation? What are the two types?
The accumulation of many nerve impulses resulting in a meaningful response. // SPATAIL- number of synapses firing at one time // TEMPORAL - one synapse repeatedly firing
Are potassium or sodium ion channels exciatatory or inhibitory ?
Potassium -> inhibitory, bringing neurone further from threshold repolarisation
Sodium-> excitatory , bringing neurone closer to the threshold
What is meant by an excitatory postsynaptic potential? (EPSP)
A graded depolarisation caused by a neurotransmitter arriving at a postsynaptic threshold *if enough are added together a threshold potential is reached
What determines the speed of a nerve impulse?
Axon diameter// Myelinated fibres
What area of the brain are involved in which functions?
PREFRONTAL CORTEX - problem solving / complex planning/ personality // MOTOR CORTEX - planning control/ executing voluntary control / movement // BOROCAS AREA- speech// OCCUPITAL LOBE - visual processing // TEMPORAL LOBE - processing sensory information (hearing/speech..) // WERNIKE’S AREA- language comprehension ///
Describe the functional organisation of the nervous system.
- SENOSRY(afferent) -> transmits information -> somatic sensory and visceral sensory // 2.MOTOR (efferent)-> somatic and autonomic motor
What is the role of each division of the nervous system ?
SENSORY (afferent) -> transmits info from periphery to CNS + contains receptors // MOTOR (efferent) -> transmits info from CNS to the body + sends motor info to effectors // SOMATIC SENSORY -> receives info from skin, joints, skeletal muscles… // VISCERAL SENSORY -> receives sensory info from viscera// SOMATIC MOTOR -> voluntary nervous system controlling skeletal muscles // AUTONOMIC MOTOR -> involuntary nervous system e.g. cardiac, smooth muscle and glands
Why are reflex circuits suited to control and protective functions?
CONTROL - closed loop/ stimuli feedback causes a responce,/ muscle streches creating a contraction e.g. tendon jerk // PROTECTIVE - open loop// protection form a harmful stimuli/ stimulus feedback has no effect on stimulus e.g. felxion withdrawl reflex, a pin pricks the leg the leg respondes byut doesnt change the stimuli of the pin itself
Contrast the anatomy and functions of the somatic and automatic nervous system.
SOMATIC - creates voluntary contractions (skeletal muscle ) and only involved one neurone // AUTONOMIC - creates involuntary contraction (cardiac and smooth muscle ) involving 2 neurones , pre and post ganglionic neuron
What are the 3 divisions of the ANS?
SYMPATRIC - // PARASYMPATHETIC // ENTERIC
What are some diseases associated with the ANS?
Hypertension/ heart failure/ obesity / depression/ chronic pain/ inflammation/ Alzheimer’s disease/ obstructive sleep apnoea
How can the ANS be manipulated pharmacologically to reduce disease symptoms?
MUSCARINIC ANTAGNISTS (e.g. atropine ) used in surgery to prevent parasympathetic reflexes when handling organs // BETA-ADRENERGIC ANTAGONISTIC (e.g. beta blockers ) slows heart rate
What are the main functions of the nervous system?
SOMATIC - conscious/ voluntary control of skeletal muscles// AUTONONIC - self-regulating involuntary control e.g. heart rate -> can be SYMPATHETIC (close to CNS) , ENTERIC or PARASYMPATHETIC (close to target organ)
What is meant by viscera ?
The soft internal organs of the body, including the lungs, the heart, and the organs of the digestive, excretory, and reproductive systems
What is the difference between cranial and spinal nerves?
CRANIAL originate in brain and are categorised as motor, sensory or vagus// SPINAL originate from spine and are mixed with sensory and motor nerve fibres
What is meant by dermatome ?
The area of the skin which sends signals to the brain through the spinal nerve
Give an example of a monosynaptic reflex.
Tendon jerk (knee jerk )
1. sensory receptor detects muscle stretch // 2. info passes along sensory (afferent ) neurone ) through spinal cord to the motor (efferent ) neurone)// 3. causing effector (quadriceps) to change in length and create a response
What is the difference between a monosynaptic and a polysynaptic reflex?
Monosynaptic - contains one synapse between a sensory (afferent) and a motor(efferent) neurone // Polysynaptic - one or more interneuron connect afferent to efferent neurones
What is the main difference between the somatic and automatic efferent pathway?
-both originate from sensory neuron in the spinal cord and leave via a ventricular route // Autonomic nerve involves two neurones (post and preganglionic neurone) // somatic nerve involves a singular neurone
With reference to reflexes how is blood pressure reduced at high blood pressure?
1.Baroreceptors detect high blood pressure //2.info is sent to medulla// 3. reduces sympathetic impulse- dilating arteries therefore increasing blood flow , reducing blood pressure// 4.Increased parasympathetic pathway , reducing heart rate and cardiac output – Blood pressure is reduced
*same mechanism works in a backwards order
What is the location and function of the adrenal medulla ?
Located - above kidneys within the adrenal gland// function - produce adrenalin and noradrenaline
What does the release of adrenaline result in?
Acts on adrenergic receptors , activating organs supplied by postganglionic sympathetic neurones (blood vessels , liver, bronchi, pupils…) // Also acts on other organs including skeletal muscles
