SNAB topic 8- investigating brain function

Identify the location and function of the medulla oblongata.

Controls a range of autonomous functions, including breathing and heart rate (location of cardioacceleratory / deceleratory centres).

Identify the location and function of the cerebellum.

● Controls execution (not initiation) of movement e.g. timing, balance, coordination, posture.

● Possible role in cognition e.g. attention & language.

Identify the location and function of the hypothalamus.

● Includes anterior pituitary gland (secretes metabolic & reproductive hormones).

● Involved in thermo & osmoregulation.

What is the cerebrum?

Largest part of the brain. Composed of two halves (cerebral hemispheres) connected by a band of nerve fibres (corpus callosum). Different lobes have different functions to control advanced mental activity e.g. vision, thought, learning.

Name the main cerebral lobes and state their function

● Parietal lobe at the top of the brain: movement, orientation, memory, recognition.

● Occipital lobe at the back of the brain: visual cortex processes signals from the eye.

● Temporal lobe beneath the temples: processes auditory signals.

Name 4 medical imaging tools used to investigate brain structure and function.

● Magnetic resonance imaging (MRI).

● Functional magnetic resonance imaging (fMRI).

● Positron emission tomography (PET).

● Computed tomography (CT) scans

How does an MRI scan work?

Uses powerful magnetic field to cause protons from hydrogen atoms in water molecules to align. Radio waves then knock protons out of alignment. When protons realign after radio waves turn off, they emit radiation to receivers. Signals are used to produce a cross-sectional image

How can an MRI scan be used in diagnostics?

For soft tissue, shows:

● Excess fluid

● Diseased structures

● Size & position of tumours

Suggest the advantages and disadvantages of using an MRI scan.

+ High resolution distinguishes between tissues

+ 3D image or cross-section

+ No radiation = comparatively safe

- Image affected by movement

- Does not show bone

How does an fMRI scan work?

Uses MRI technology to study brain activity based on blood flow. Oxyhaemoglobin absorbs high frequency radio signals; deoxyhaemoglobin reflects them. Shows where most aerobic respiration occurs. Active areas have higher respiratory rate.

How can an fMRI scan be used in diagnostics?

Shows abnormal patterns of activity in the brain e.g. related to seizures.

Suggest the advantages and disadvantages of using an fMRI scan.

+ Can investigate normal functioning of the brain.

+ No radiation = comparatively safe.

+ Suitable for use in real time.

-Difficult to interpret results; one brain region may be responsible for a variety of processes.

-Cannot show action of individual neurons.

How does a PET scan work?

A radioactive isotope e.g. of carbon is injected & used by the body to synthesise molecules. When isotope decays, it emits gamma radiation to a detector. Active areas show higher radioactivity. This allows for imaging of metabolic processes in the brain.

How can a PET scan be used in diagnostics?

● Shows tumours.

● Shows amyloid plaques associated with Alzheimer’s disease

Suggest the advantages and disadvantages of using a PET scan.

+ Can investigate normal functioning of the brain.

+ Suitable for use in real time.

+ Can show how a disease progress over time

- Gamma radiation is harmful.

How does a CT scan work?

Uses X-rays to produce cross-sectional image. Denser structures absorb more radiation and appear lighter on image

How can a CT scan be used in diagnostics?

Bleeds appear white on image e.g. after a stroke.

Suggest the advantages and disadvantages of using a CT scan.

+ Non-invasive and quick

- X-rays are a mutagenic agent.

- Can only be used to investigate abnormal functioning of brain.