The nervous systems and brain cells Flashcards
What does human physiology do?
Promote Homeostasis
Keeps all body cells happy:
There have to be conditions for cells to operate and stay alive to do their jobs
We need:
Oxygen
Nutrients & Water Balance
H+ levels (pH = 7.4)
Temperature 37.2 C
Rid waste products
If deviate from these conditions, cells wont operate properly
What happens if pH levels vary?
- Cells can only function correctly in the right environment
If the pH goes out of a specific range, cells start to die or perform badly - pH (Acidity and Alkalinity) can greatly affect how a cell functions
- Too acidic (acidosis)- neurons are unable to send messages
- Too basic (alkalosis) - neurons send uncontrolled messages
In both situations we have suboptimal performance - Death results if pH levels are out of the range of 6.8 to 8.0
What are the 2 nervous systems and their composition?
Central (CNS):
Cerebrum
Cerebellum
Brain Stem
Spinal Cord
Peripheral (PNS): All nerves outside of the spinal cord
Somatic NS
Autonomic NS
What is the somatic nervous system made of?
- The somatic nervous system receives sensory input and delivers motor/muscle output
Make motor commands to react to inputs from the env - Sensory input is received through the dorsal roots to the spinal cord
- Motor output is delivered via the ventral roots of the spinal cord to the muscle
- There are 6 areas that the nerves join the CNS - cranial, cervical, thoracic, lumbar, sacral, coccygeal
- There are 4 lobes of the cerebrum (frontal, parietal, occipital, temporal)
- The brain receives sensory information (of touch) at the somatosensory cortex and produces behaviour by modulating motor output from the primary motor cortex
What is the autonomic nervous system made of?
- Sympathetic: extends from thoracic and lumbar spine
- Short preganglionic nerves
- Long postganglionic nerves
- Parasympathetic: extends from cranium and sacral spine (craniosacral)
- Long preganglionic nerves
- Short postganglionic nerves
- Both are usually active - but change intensity as the need arises
- Parallel systems that work in opposition to each other (when 1 aug, the other dim)
- Increase sympathetic results in decreased parasympathetic
- Sympathetic - four F’s, Parasympathetic - non emergency (digestion, growth, immune responses, energy storage)
4 Fs: fight, flight, fornication, fright, if there are threats in the env or basic needs that need to be satisfied
How does the brain and body communicate?
- Peripheral Nervous System
- Somatic (sensorimotor)
- Autonomic (parasympathetic, sympathetic)
- Hormones (have many diff fctions)
- Hypothalamus & Pituitary (many different hormones)
- Pineal gland (melatonin)
- Consider: speed and range of effect
PNS = immediate reactions, targeted
Hormones = slower response and has wider range of effects (not targeted)
How do we keep the brain happy?
- The brain is highly vascularised (ie has many arteries and veins) which maintain a constant fresh supply of oxygen & nutrients (glucose) to the brain cells
The cells need energy and O2 to perform their fctions - The brain is protected and nourished in several ways:
- The Blood Brain Barrier (BBB)
- Cerebrospinal Fluid (CSF)
- Glial cells
How do we cross the blood brain barrier?
- Brain capillary endothelial cells have continuous tight junctions
- Only highly lipophilic drugs and small uncharged molecules can cross from blood capillaries to cerebrospinal fluid (CSF) by diffusion
- Important nutrients-amino acids & glucose are actively transported across to CSF by proteins in the capillary membrane called TRANSPORTERS. Transportation across the membrane requires energy use.
How does CSF protect the brain?
- Cerebrospinal fluid (CSF) is made by the choroid plexus (in lateral & third ventricles)
- The ventricles and subarachnoid space circulate cerebrospinal fluid through and around the brain to provide nourishment and protection (cushioning) of neural tissue
- There are four ‘ventricles’ (lateral, third, fourth, cerebral aqueduct)
- Once CSF has circulated around the brain it is reabsorbed by the arachnoid villi (of subarachnoid space) into venous blood (return to heart)
- The cranial and spinal meninges also protect and nourish these areas: dura mater, arachnoid mater, pia mater.
How big is the neuron network?
The human brain (starts with!) has approx 100 billion neurons (and even more glial cells!!)
HUGE network for communication & complex processing
Activity needs to comm, coordinate and time their activations to prod cognition
What are 4 types of brain cells?
- Neurons
- Glial cells - astrocytes & oligodendrocytes
- Ependymal cells - line the CSF-filled ventricles (neurogenesis)
- Microglia - remove dead or degenerating neurons or glia (phagocytosis)
What are the 4 main parts of neurons?
Soma (cell body)
Dendrites
Axon Presynaptic
Terminals
What are 5 ways to classify neurons?
- The number of Neurites (from cell body)
- Their dendrites - how many and if they have spines or not
- Their axon length
- The neurotransmitter used by the neuron
- Neuronal connections - primary sensory neurons or motor neurons
How do we classify neurons by neurites?
Cells can be unipolar, bipolar or multipolar - defined by the number of neurites connected to the soma
An apical dendrite extends from the apex of the pyramidal cell soma Basilar dendrites are connected to the base of the soma (not the axon)
How do we classify neurons by their dendrites?
Neurons are classified by the shape and kind of dendrites
* Stellate (starshaped) vs pyramidal (triangular)
* Has spines (spinous) or doesn’t have spines (aspinous)
* Dendritic spines are involved in learning and memory
* Dendritic trees constantly change (grow or receed) - aids in neuroadaptation
* Dendrites are sources of information for the neuron - the more dendrites the more info the neuron receives
