Nervous system Flashcards
What percentage of total body weight does the brain make up?
2%
How many neurons is the brain roughly comprised of?
86 billion
What is the cerebrum?
The largest and most superior structure of the CNS
What 2 structures does the cerebrum contain?
Cerebral cortex
Basal ganglia
What are the two hemispheres of the cerebrum connected by?
Corpus collosum
What are the crests of folded tissue in the brain called?
Gyri
What are the grooves/fissures in the brain called?
Sulci
What are the four lobes of the cerebral cortex?
Frontal
Temporal
Parietal
Occipital
Where is the motor cortex?
In the frontal lobe, anterior to the central sulcus
What is the motor cortex responsible for?
Voluntary motor control and deciding/planning actions
What is the role of the primary motor cortex (M1)?
Motor commands to motor neurons, initiation and coordination of voluntary movements
What is the role of the premotor cortex?
Organisation of movements before they are initiated
What is the role of the supplementary motor area (SMA)?
Preparation and control of sequential movements
Where is Broca’s area?
The frontal left area
What is the role of Broca’s area?
Contains neurons involved in speech and language
How is the motor cortex organised?
Somatotopically
What is somatotopic organisation?
Relating to the movement capacity of the body
What are the basal ganglia?
A set of subcortical neural nuclei strictly interconnected with the cortex and the brainstem
What five areas does the basal ganglia include?
Striatum (caudate and putamen)
Globus pallidus
Substantia nigra
subthalamic nucleus
Nucleus accumbens
What is the role of the basal ganglia?
Important in the control of voluntary movements, motor learning, cognition and emotion. Proper functioning of the basal ganglia are required to relay motor commands to the lower levels
What are the two pathways involved in basal ganglia connectivity?
Direct pathway
Indirect pathway
What is the direct pathway of the basal ganglia involved in?
The excitation of a desired motor programme
What is the indirect pathway of the basal ganglia involved in?
Inhibition of a competing motor programme
What is the cause of Parkinson’s disease?
Degeneration of neurons in the substantia nigra. It causes an increase in activity in the indirect pathway, and a decrease in activity in the excitation motor cortex
What are the symptoms of Parkinson’s disease?
Likelihood of falling, shuffling gait, tremor at rest (less voluntary movements), slowness of voluntary movements (bradykinesia), difficulty in initiating movements (akinesia), inadequate amplitude of movements (mypometria)
What is the cause of Huntington’s disease?
Selective loss of striatal neurons. This causes an increase in activity in the direct pathway, and a decrease in activity in the inhibition motor cortex
What are the symptoms of Huntington’s disease?
Choreiform movements: involuntary (dyskinesis), continuous movement of the body, especially extremities and the face (more voluntary movements, but with less control). Resemble adaptive movements, but occur involuntarily and incoherently
Where is the cerebellum located?
Prominent structure situated at the back of the pons (brainstem)
What is the role of the cerebellum?
Concerned with motor coordination, posture and balance. Plays a fundamental role in the execution of smooth and accurate movements
What percentage of the brain’s volume is the cerebellum?
10%
What percentage of brain neurons does the cerebellum contain?
Over 50%
Where does the cerebellum receive input from?
The sensory system (vestibular and somatosensory in particular)
The motor cortex
How is the cerebellum involved in motor commands?
It modifies the motor commands of the descending pathways to make movements more adaptive and accurate
What are the four roles of the cerebellum?
Maintenance of balance and posture
Coordination of voluntary movements
Motor learning
Cognitive functions
How does the cerebellum maintain balance and posture?
Adjusts posture in order to maintain balance.
Receives input from vestibular system and proprioceptors.
Modulates commands to motor neurons to compensate for shifts in body position or changes in load upon muscles.
How does the cerebellum coordinate voluntary movements?
It coordinates the timing and force of different muscle groups to produce fluid limb or body movements
In which lobe is the somatosensory cortex located?
Parietal lobe
Where is the primary somatosensory cortex (SI) located?
Posterior to the central sulcus, on the postcentral gyrus of the parietal lobe
Where does the primary somatosensory cortex receive input from?
The thalamus, relayed from the periphery via the spinothalamic tract
How is S1 organised?
Somatotopically, with the body and face mapped contralateral to the side of the body
Which aspects are represented medially and laterally in S1?
The tongue laterally, the feet medially
What is S1 principally associated with?
Identification of shape, size and texture
Which 3 areas do S1 neurons communicate with?
Secondary somatosensory cortex, posterior parietal cortex, motor cortex
Where does S1 relay info to?
M1
Where is the secondary somatosensory cortex located?
The lateral wall of the Sylvian sulcus
What is SII important in?
Tactile object recognition, as well as tactile learning and memory
What 4 places does SII have connections with?
S1, motor cortex, insular, posterior parietal cortex
What does damage to SII cause?
Deficits in learning through object manipulation
What is the posterior parietal cortex?
A multisensory association area that integrates sensory information, including vision, somatosensory and auditory inputs
What 2 things is the PPC involved in?
Control and error correction in movement, movement planning to achieve a motor goal
What is a stroke?
An alteration in blood flow in the CNS, resulting in neurological deficit lasting more than 24 hours
