Lecture 2 - Introduction to Neurophysiology Flashcards
Central nervous system
Brain and spinal cord
Peripheral nervous system
Cranial nerves and the spinal nerves (peripheral nerves)
Both the CNS and PNS are made out of
Neurons and glia
CNS =
Somatic nervous system and autonomic system
PNS =
Somatic sensory division (afferent), somatic motor division (efferent), visceral sensory divison (afferent), sympathetic division (efferent), the parasympathetic division (efferent) and the neuroendocrine division
Somatic nervous system is …
Voluntary
innervates things like our skeletal muscles
Autonomic nervous system is …
involuntary
innervates things like our cardiac muscle, smooth muscle, glands, adipose tissue
Somatic sensory divison
Afferent
responsible for relaying information from the body to the CNS
Somatic and special receptors
Somatic motor division
Efferent
responsible for sending out commands from the CNS to the body, stimulating muscle contraction
Somatic effectors (skeletal muscle)
Visceral sensory division (afferent)
Autonomic
Visceral receptors receive stimulus that get sent to the CNS
Sympathetic division efferent
Autonomic
Fight or flight response
Prepares body for stress responses. Effects include - increased heart rate, constricting blood vessels to skin and viscera to increase blood flow to muscles, decrease digestion, decrease salivation, increase pupil size and increase sweating
Parasympathetic division efferent
Autonomic
rest and digest response
Prepares body for restful situations. Effects include decreased heart rate, increase in gastric motility, decrease in pupil size, increase in salivation
Overview of spinal reflex arc
Stimulation of receptor
Activation of sensory neurons
Information processing in the CNS
Activation of motor neuron
Response of peripheral effector (agonist muscle is contracted, there is also inhibition of the antagonist muscle)
Integration of the information from the spinal reflex arc
stimulus - afferent input via the dorsal root ganglion - up to the brain - modification of the response and travels back down (the afferent signal into the brain CROSSES at the spinal cord i.e. the stimulus is recorded in the brain at the opposite side of the brain that the stimulus was recorded
Stretch reflex and withdrawal reflex are part of the spinal reflex arc
Stretch reflex
Muscle spindles/stretch receptors are stimulated when the muscle is stretched. Results in nerve fibre activation and impulses sent from spindles to the spinal cord along afferent fibres. Information is processed at the level of the spinal cord which causes activation of motor neurons which causes innervation/contraction of the muscle in order to prevent overstretching
Withdrawl reflex
Painful stimuli triggers APs up afferent pain fibres which synapse in the spinal cord. Signals go up to brain to alert of pain, to other levels of the spinal cord to coordinate movement of other joints and onto efferent motor fibres within that spinal level. Stimulation of flexors and inhibition of extensors allows doe withdrawal away from the painful stimulus
Lobes of the brain and their roles
Each side of the brain has four lobes
Frontal lobe = motor cortex plus behaviour, mood, personality, language
Parietal lobe has the somatosensory cortex and also the association cortex (faces, shapes, words etc.)
Temporal lobe = hearing and memory
Occipital lobe = vision
Prefrontal cortex
cerebral cortex that covers the front part of the frontal lobe, principal function is aggression and emotion
Basal ganglia (includes thalamus)
Voluntary movement
Hypothalamus
Neuroendocrine and autonomic control
Brainstem (including pons and medulla)
Autonomic/somatic regulation
Cerebellum
Integration of sensory and motor information for smooth controlled movement
Reticular formation
Arousal
Limbic system
(includes amygdala and hippocampus) = language, learning, emotion, short and long term memory
Corpus callosum
(part of the limbic system) = communication between the two hemispheres
Primary motor cortex
Precentral gyrus
Primary somatosensory cortex
Postcentral gyrus
Primary motor cortex organisation
the precentral gyrus functions as the primary motor cortex, specific regions of the motor cortex control specific regions of the body
In the frontal lobe
Larger area on brain = highly innervated body part (e.g. face and hands)
Towards sulcus is foot and as you go along the gyrus you progress vertically up the body
Primary somatosensory cortex organisation
Postcentral gyrus functions as the primary somatosensory cortex, specific regions of the somatosensory cortex receive sensory information from specific regions of the body
In the parietal lobe
Larger area on brain = high sensory innervated body part (e.g, hand, lips, tongue)
Towards sulcus is foot and as you go along the gyrus you progress vertically up the body
Autonomic nervous system neurons organisation
3 neurons between the brain and effector
Neuron 1 = cell body in brain with axon in brain or spinal cord
Neuron 2 = preganglionic neuron: cell body in brain or spinal cord with myelinated axon in PNS (autonomic ganglion) (neurotransmitter = ACh)
Neuron 3 = post ganglionic neuron: cell body and axon in the PNS (autonomic ganglion) extending to the effector ( neurotransmitter = ACh or Norepinephrine)
Sympathetic neurons
Preganglionic neuron has short axon
Autonomic ganglion is close to the CNS
Postganglionic neuron has long axon
Release ACh at ganglion, releases NE at the effector (except sweat glands which is ACh)
Parasympathetic neurons
Preganglionic neuron has a long axon
Autonomic ganglion is distant from the central nervous system
Post ganglionic has a short axon
Release ACh at ganglion, releases ACh at effector
Somatic efferent (motor) division neurons
Neurotransmitter = ACh
Two neurons between brain and effector (skeletal muscle)- Upper motor neuron (cell body in brain, axon in spinal cord, myelinated- oligodendrocytes because CNS) and the lower motor neuron (cel body in spinal cord, axon in spinal nerve, myelinated - Schwann cells because PNS)
Neurons
Excitable - K+ and Na+ ion channels, Na+/K+ ATPase, transporter, synapse specialisation
Axon, dendrites, synapse
Neurons are a specialised type of cell that transmit information
Glia function
Maintain local environment and are involved in metabolism (support cells)
Myelin to help with nerve conduction, cerebrospinal fluid is maintained by these cells
Non-excitable but do have a resting membrane potential - K+ channels, Na+/K+ ATPase, transporters, transporters for support
Types of glia
Astrocytes, oligodendrocytes, ependymal cells, microglia
Astrocytes
maintain microenvironment and form part of the blood brain barrier
Oligodendrocytes
(and Schwann cells which are in the PNS) - wrap around the axon to form the myeline sheath
Ependymal cells
form the ventricular epithelium ( ventricles are the fluid filled spaces in the brain that contain the cerebrospinal fluid), lines the fluid filled spaces in the brain and spinal cord to circulate CSF with their cilia
Microglia
Mount the CNS immune response
Nerves
primary role is to provide a pathway to conduct electrical impulses throughout the body. It essentially relays information from one part of the body to another.
Three layers of connective tissue = axons covered in endoneurium, fascicles (bundles of axons) covered in perineurium, nerves are covered with epineurium
Multiple icons are bundled to form fascicles
Fasicles bundle together to form a nerve
Axons are covered with
Endoneurium
Fascicles are covered in
perineurium
Nerves are covered in
epineurium
Electrical synapse
Communication is very fast, ions flow from cell to cell
Gap junctions
Chemical synapse
Slower communication, relies upon chemical crossing the gap
Complex series of events
Neurotransmitter packaged in vesicles
Synapse strength can be modified
Afferent neurons
sensory neurons that carry stimuli towards CNS
Efferent neurons
motor neurons that carry neural impulses away from CNS and towards muscle to cause movement
Dorsal spinal cord
Sensory/afferent
Ventral spinal cord
Motor/efferent
Autonomic ganglion
collection of cell bodies in the PNS
Saltatory conduction
Between nodes of ranvier, increases speed of action potential
Somatic nervous system has what as a part of the system
the dorsal root ganglion is part of the somatic sensory nervous system
Interneuron in reflexes
Interneuron between afferent and efferent - afferent synapses onto the interneuron and the interneuron communicates with the efferent fibres of what to do, interneuron sends information to the brain for processing
