Theme 3 Flashcards
How do the mechanoreceptors function?
Detect physical changes in their receptors
Define encapsulated
Free nerve ending wrapping around the hair
- What is the type of sensory receptor shown?
- What type of sensory fibres does it use?
- What does it sense?
- Hair Follicle Receptors
- A-beta
- Motion & direction
- What is the type of sensory receptor shown?
- What type of sensory fibres does it use?
- What does it sense?
- Free Nerve endings
- A-beta & C fibres
- Pain
- What is the type of sensory receptor shown?
- What type of sensory fibres does it use?
- What does it sense?
- Meissner corpuscle
- A-beta
- Tap & Flutter (5-40hz)
- What is the type of sensory receptor shown?
- What type of sensory fibres does it use?
- What does it sense?
- Merkel cells
- A-beta
- Touch & Pressure
- What is the type of sensory receptor shown?
- What type of sensory fibres does it use?
- What does it sense?
- Pacinian corpuscle
- A-beta
- Vibration 60-30hz
- What is the type of sensory receptor shown?
- What type of sensory fibres does it use?
- What does it sense?
- Ruffini corpuscle
- A-beta
- Skin stretch
How does a rapid adapting receptor differ from a slow adapting receptor?
Rapid Adapting: ADAPTs = no maintained stimulus
- responds to the application and removal of a stimulus
Slow adapting: Slow adapting receptors remains active for the duration of a maintained stimulus.
List some example of rapid adapting and slow adapting receptors.
Rapid Adapting Receptor:
- Meissner Corpuscles
- Pacinian Corpuscles
Slow Adapting Receptors:
- Merkel cells
- Ruffini Corpuscles (Some hair follicle receptors for both)
Define Receptive field
area in which a nerve cell sends its receptors and can pick up information from the skin
What is Lateral inhibition?
Ability of activated neurones to inhibit neighbours - inhibiting the outside of a receptive field
In terms of the number of sensory receptors and size of receptive fields, how does the skin on the back of a person differ from the skin on the fingertips of a person?
Receptors on back are fewer with larger receptive fields.
Receptors on fingertips are more numerous with smaller receptive fields - highly discriminatory
What effect does the convergence of some pathways have?
Increases the efficiency and sensitivity to see something, but reduces the discrimination
What is the function of an Alpha-motoneuron?
Activation of skeletal muscle fibres
Branch extensively
What are the different musculature in the lower spinal cord?
Distal musculature: controls fine movements e.g. fingers
Proximal & Axial musculature: controls position
What is the difference in function between the muscle spindle and the golgi tendon organ?
Muscle spindle stimulates muscle contraction, whereas golgi tendon organ inhibits muscle contraction.
What would happen if the lower motor neurones are harmed?
Flaccid paralysis
What happens if the Upper motor neurones are harmed?
Spastic paralysis, as lower motor neurones are still active
Which reflex might be acting when an arm adjusts to carrying an increased load?
Which type of afferent fibres are involved in the stretch reflex?
Stretch reflex
1a fibres
Which reflex will act to release strain on a tendon when it is being overstretched? How?
Inverse stretch reflex/inverse myotatic reflex/ 1b tendon reflex
stimulates activation of the antagonistic muscle. Opposite to simple stretch reflex
How do tendon & stretch reflexes work together?
Oppossite effect to each other
Tendon damps down stretch reflex = prevention of excessive muscle contraction
What is a central pattern generator?
programmed movements (e.g. chewing, swallowing) regulated by local C.P.Gs in spinalcord/brainstem
What are each of the four brodman areas of the cortex responsible for?
Area 1: Cutaneous stimulus
Area 2: touch and proprioception (size and shape)
Area 3a: Proprioception
Area 3b: Cutaneous stimulus and Primary Somatosensory cortex
Where is the primary somatosensory cortex?
Postcentral gyrus
Where is the Secondary somatosensory cortex located?
Gyrus next to post-centre gyrus
Where are the upper motor neurones found?
Cerebral cotex
What are the direct pathways from Upper motor neurones to lower motor neurones?
Corticospinal tract
Corticobulbar tract
What happens if the direct & indirect pathways are damaged?
DP: Paresis (weakness), paralysis (total loss) Local reflexes will still be present, only damaged descending stuff not locally
IDP: Act on spinal reflexes - Damage: spastic paralysis
What is the corticobulbar tract responsible for innervating?
Motor nuclei of cranial nerves V, VII, XI, and XII
What is the ‘babinski sign’, and what does it indicate when present in adults?
stroking the sole of the foot causes an abnormal fanning of the toes and the extension of the big toe. There is damage to the direct pathway - upper motor neurons (corticospinal and corticobulbar tracts)
What does damage to the basal ganglia cause?
causes movement disorders – e.g. too much movement or too little movement depending on where damage is located
Define Reticular Formation.
What is the role?
Functions?
all the neurones, in pons or medulla, that are not in specific nuclei/ axons that are not in a specific pathway
Role:
- Lots of nuclei/area/clumps of nuclei, that send fibres up into cortex where they release neuromodulators – things that are not directly conveying information but excite stuff
- Down to spinal cord: where it controls patterned activity
Functions:
- Cranial nerve activity
- Slow pain conduction and modulation
- Voluntary movements
- Autonomic nervous system activity
- Respiration
- Sleep
Which 4 cranial nerves carry parasympathetic preganglionic fibres?
III, VII, XI, X
What is the nucleus of CNIII?
Edinger-Westphal nucleus
Where do all the pain fibres in the head & neck end up?
spinal trigeminal nucleus
What is tooth pain mediated by?
Plexus of Raschkow - central plexus in the pulp of each tooth
Where are A & C fibres found in the teeth?
A: dentine tubules
C: Centre of pulp
What is the Anterior Cingulate Cortex (ACC) responsible for in the processing of pain?
Emotional association with pain
Which nerve is responsible for initiating the Corneal reflex when the cornea is touched?
V1 - Opthalmic → Spinal nucleus of V → Facial motor nucleus → Orbicularis Oculi
Which nerve is responsible for initiating the gag reflex when the back of the oropharynx is touched?
Glossopharyngeal nerve → vagus nerve
How is the jaw unloading reflex essential in mastication?
After biting down with force upon an object, the muscles of mastication relax to ensure the teeth don’t ‘crash’ into each other
What’s the purpose of the Masseter-Hypoglossal reflex?
Prevent the tongue being bitten
What are the Sensory neurones from retina to brain?
Retinal ganglion cells
Why is the Retinal pigmented epithelium black?
What would happen if it was not black?
helps to absorb any spare light that hits the back of the retina – absorbing any light that is not picked up by the photoreceptors
If it was translucent/reflective, light would bounce of and trigger multiple photo receptors = multiple images of one object would be shown
What is the pathway in the retina?
Light –> Pigmented Epithelium –> Rods/Cones –> Bipolar cells –> Retinal Ganglion Cells
What are the 2 types of photoreceptors?
How much light is needed to activate each?
Rods: black & white receptors – more sensitive to light (less light)
Cones: colour receptors (more light)
- How many rod cells converge onto one bipolar cells?
- What is the advantage of the lower light levels hitting multiple rods?
1.
3 = more likely that the bipolar neurones will be activated and will send signals onto the retinal ganglion cells
2.
Lower light levels will hit multiple rods which will feed in, the signal will be amplified into the bipolar cells so black and white can be seen in much lower light levels.
= Due to convergence, objects and shapes will be identifiable but not able to distinguish.
What is the function of amacrine cells in the retina of the eye?
Modulation of an image based on the turning on/off of retinal ganglion cells
What is the photoreceptive pigment found in the rods and cones of the retina?
Membranous disks
Rods: Rhodopsin
Cones: Photopsin
What G-protein does rhodopsin activate when hit by light?
Transducin
What nucleus do the motoneuron fibres that are innervated during the pupillary light reflex originate from?
Edinger-Westphal nucleus - also contorls the iris
Two main reflexes of the eye
Pupillary Light Reflex: Light shone into one eye = contraction both pupils
- Constriction pupil same eye – direct light reflex
- Constriction pupil opposite eye – consensual light reflex
Accommodation Reflex: Focus on near/incoming object
- Pupillary constriction
- Convergence eyes
- Focussing of eyes on near object
How does information hit the visual fields of the eyes?
Eyes respond to opposite sides
Optic nerve pathway
Visual field hits both the receptors
Left visual field: L.nasal side & R.lateral side - both go to optic chiasm
Right visual field: R.nasal side & L.lateral side
Nasal fields (1/2 of VF) will cross over to the opposite side of chiasm
What are the different lesion problems?
Full dark circle = no eye vision
Half dark circle = loss of vision on opposite side
What are the semicircular canals?
filled canals
Orientated in Horizontal, vertical and coronal planes = all movements are picked up – movement of the fluid over the hair cells is picked up
How is an action potential generated in the ear? (conversion of sound)
Vibration in the stapes, generates motion in the perilymph fluid depending on the frequency
leading to vibration in the Basilar membrane
as it vibrates the Tectorial membrane will move across the hair cells – moving them – opens ions channels = AP
Name the receptor organs responsible for detecting vibrations in the basilar membrane, and hence detect sound & Name the nerve that it innervates
Organ of Corti
Cochlear nerve (part of vestibulocochlear nerve)
Name the fluid found within the cochlear that transmits vibrations.
Endolymph fluid
- Which type of cell found within the auditory receptor organ provides the sensory transduction of sound?
- What are the sensory projections on these cells known as?
- Inner hair cells
- Stereocilia
Name the receptor organs responsible for sensing balance. (Where are they located)
Ampullae - located in the Semicircular canals
Name the two otolith organs and their function
Utricle + Saccule, sensing tilting of the head.
Which brainstem nuclei does sensory (vestibular) information from the vestibular nucleus transmit to?
Cranial nerve nuclei: III, IV, VI
What is the auditory pathway?
(Orders of nuclei
1st: Synapses in brainstem
2nd: –> Superior Olivary nucleus –> Inferior colliculus
3rd: –> Medial geniculate nucleus of the thalamus
What is the Auditory stream?
Pathways allows response to auditory stimulus = understanding speech and provides a response
Primary auditory cortex
Association auditory cortex
Wernicke’s area: understanding speech
Arcuate fasciculus
Broca’s area: speaking
Motor cortices
What is the difference between Cortical & Cord patterns?
Cortical: complex; also, they can be “learned”
Cord: determined by heredity and are said to be “hard wired.”
What function does the prefrontal association cortex have in general movement?
Integration of motor information and decision making
List the outputs of the supplementary motor cortex. (4)
- Corticospinal tract
- Corticobulbar tract
- Reticular formation
- Primary Motor Cortex
The front part of the supplementary cortex is involved in motor functions of the face. True or False?
True
The lateral part of the Primary Motor Cortex is involved in the movement of facial muscles. True or False?
True
Which area of the brain is responsible for assessing the context of a situation and creating an internal model of the movement that is about to be made?
Posterior Parietal Cortex - receives somatosensory, proprioreceptive, and visual inputs
Which pathways carry visual information from the visual cortex to the rest of the brain?
Dorsal and ventral stream
What can result from damage to the Posterior Parietal Cortex?
Sensory neglect of one side of their field of vision.
What is the role of the Pre Fronal Areas?
Decisions are made about what action to take Concerned with personality, intellect, ETC.
What is the role of (pre-motor area) Area 6?
Informed about the kind of action to take by posterior parietal and prefrontal areas determine the characteristics of the movement for this purpose.
What is the function of the Cerebellum?
ipsilateral controls over the body
What are deep cerebellar nuclei of the:
- Cerebellar hemisphere
- Vermis
- Intermediate site
- Dentate
- Fastigal
- Interposed
Which pathways are involved in planning and prediction of movement through the cerebellum?
Corticopontine and pontocerebellar tract
Which brainstem nuclei are involved in the adaptation of movement in response to changes in external stimuli?
Red nucleus and Olivary nucleus
Which pathway supplies auditory and visual input to the cerebellum?
Tectocerebellar tract
What is the function of climbing fibres within the cerebellum?
Control motor responses/ real time decision making
What is the function of the Neocerebellum, and hence where is its output?
initiation and planning of movements
and hence gives an output to the premotor cortex, and supplementary motor area.
Which cells in the cerebellum are responsible for learned motor actions (muscle memory)?
Purkinje cells
What is the function of the Vestibulocerebellum?
Posture and Balance
What are the two main circuits through the basal ganglia?
Putamen circuit: Subconscious execution of learned patterns of movement Caudate circuit: Cognitive planning of movement
Which structure of the basal ganglia is affected, in:
- Parkinson’s Disease
- Huntington’s Disease
- Substantia Nigra
- Globus Pallidus
What determines motor behaviour? What disorders are associated with this?
Balance between:
Hypokinetic disorders:
- insufficient direct pathway output
- excess indirect pathway output
Hyperkinetic disorders:
- excess direct pathway output
- insufficient indirect pathway output
Which receptors are involved in the control of masticatory force & how?
Peridontal ligament receptors by inhibition of neurones in the motor nucleus of V
Where is the reticular formation found?
Found as a tract at the back of the brainstem, descending from the midbrain to medulla.
Which parts of the CNS does the reticular formation receive afferent inputs from?
Afferent = sensory
- Spinal cord
- Cerebellum
- Cranial nerves
- Forebrain
List the five major functions of the reticular formation.
- Sleep and consciousness
- Somatic motor control (through CPGs)
- Cardiovascular control
- Pain modulation
- Habituation (gradual adaptation to changes in environment)
Name the 4 nuclei of the reticular activating system, and which neurotransmitters do they produce?
- Locus coeruleus - Noradrenaline
- Raphe nucleus - Serotonin
- Ventral tegmental area - Dopamine
- Basal Forebrain - Acetylcholine
Which of these nuclei are involved in the reward pathway?
Ventral Tegmental area
How does REM sleep differ to nREM sleep
REM sleep
- involves paralysis of most voluntary muscles, and an active brain.
nREM sleep
- involves lowering of body temperature, movement of muscles, lowering of heart rate.
Define the role of the Limbic system
Neuronal circuitry that controls emotional behaviour and motivational drives (eating, drinking, sexual behaviour etc)
How does the Hypothalamus relate to the Limbic system?
Control many internal conditions of the body – vegetative & endocrine functions
What part of the hypothalamus is responsible for sexual behaviour in females?
Ventromedial hypothalamus
Neurones in the pre-optic area are responsible for which functions of the hypothalamus?
Temperature regulation and sexual behaviour in males
How does the function of the Lateral Hypothalamic area and the Supra-optic nucleus differ in their regulation of body water?
Lateral Hypothalamic area: thirst centre
Supra-optic nucleus: control of water secretion (ADH production control)
Which area of the hypothalamus would the satiety centre be found in?
`Ventromedial nuclei
What are the funcitions of the Amygdala? What effect might a lesion in the amygdala have on a person?
- Emotional learning and memory
- Fear and fear conditioning
- Reward
Person may be very calm and mellow emotionally, they may also be incapable of fear
Which part of the brain works in parallel with the amygdala to store emotional memory?
Hippocampus
Which five structures are essential for the reward pathway to function?
- VTA (Ventral Tegmental Area)
- Amygdala
- Nucleus accumbens
- Hippocampus
- Prefrontal cortex
