E 5.1 You must be able to label on a diagram of the brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres.
E5.2 Outline the funcyions of the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres.
E 5.3 Explain how animal experiments, lesions and fMRI (functional magnetic resonance imaging) scanning can be used in the identification of the brain part involved in specific functions.
Functional magnetic resonance imaging: a form of magnetic resonance imaging of the brain that registers blood flow to functioning areas of the brain. It is a technique that helps to pinpoint functional areas of the brain. While the MRI is scanning, the patient is asked to perform a series of activities and movements, such as reading a list or tapping fingers. The areas of the brain that correlate to these movements and activities "light up" on the scan and create an image. This information is used by surgical navigation computers in the planning of incisions, skull openings and tumor removal to minimize neurological deficits.
Benefits are that it is a non invasive proceedure and the exact part of the brain used can be easily seen.
Many experiments have been done on animals, usually primates where the skull is removed to get to the brain.
The brain must be kept alive so that it functions correctly
The animal must then be given tasks and the responses observed
There are many ethical objections to this, such as animal sacrifice for human gain
Accidents to the brain, stroke and tumours can damage specific parts of the brain, the damaged area is a lesion. From the position of the lesion, we can dertemine functions of that part of the brain by observing what the patient can no longer do.
This proceedure is as a reult of an accident and can'y be used to test for brain function otherwise.
Tumour on the brain
E5.4 Explain sympathetic and parasympathetic control of the heart rate, movements of the iris and flow of blood to the gut.
E5.5 Explain the pupil reflex
E 5.6 Discuss the concept of brain death and the use of the pupil reflex in testing for this.
Reasons to use pupils reflex to idicate brain death Reasons to not use pupils reflex to idicate brain death
1. The pupil is a cranial reflex/ ANS reflex controlled by 1. Some drugs eg Barbiturates interfere with the pupils reflex
the brain stem. If this is lost then they are likely to be 2. Nerve damage/ retinal damage may interfere with the pupil reflex
E 5.7 Outline how pain is perceived and how endorphins can act as painkillers.
Opioids bind to receptors on interneurons in the pain pathways in the central nervous system. The natural ligands for these receptors are two enkephalins
The two enkephalins are released at synapses on neurons involved in transmitting pain signals back to the brain. Instead of synapsing with a dendrite or cell body, the enkephalin synapse occurs close to the terminal of a pain-signaling neuron. The enkephalins hyperpolarize the postsynaptic membrane thus inhibiting it from transmitting these pain signals.
The drawing shows how this mechanism might work. The activation of enkephalin synapses suppresses the release of the neurotransmitter (substance P) used by the sensory neurons involved in the perception of chronic and/or intense pain.
The ability to perceive pain is vital. However, faced with massive, chronic, intractable pain, it makes sense to have a system that decreases its own sensitivity . Enkephalin synapses provide this intrinsic pain suppressing system.
Morphine and the other opioids bind these same receptors. This makes them excellent pain killers.
1. Sensation of painful stimuli
> nociceptors > mechanoreceptors > thermoreceptors
- ascending fibers transmit message of pain to various brain locations - neurotransmitter = substance P - excitatory neurotransmitter released by pre-synaptic neuron - increases Na+ permeability in post-synaptic membrane
2. Inhibition of pain