Neurons are the basic signalling units that transmit information throughout the nervous system. Neurons vary in form, location and interconnectivity and this is related to their functions. Glial cells provide structural support and electrical insulation to neurons. Dendrites are branching extensions of the neuron that receive inputs from other neurons. Spines are little knobs attached by small necks to the surface of the dendrites and are specialized processes. The axon is a single process that extends from the cell body. Transmission occurs at the synapse. Axon collaterals are combined axons. Along the length of the axons, there are evenly spaced gaps in the myelin. These gaps are called the nodes of Ranvier.Neuronal signalling is receiving, evaluating and transmitting information of neurons. Neurons are presynaptic when their axon makes a connection onto other neurons and postsynaptic when other neurons make a connection onto their dendrites. Energy is needed to generate signals, energy is in the form of an electrical potential, voltages depend on the concentrations of potassium, sodium and chloride ions and when a neuron is not signalling, the inside of the neuron is more negative than the outside.Ion channels are proteins with a pore through their centres. They allow certain ions to flow down their concentration gradients. These channels selectively permit one type of ion to pass through the membrane. Permeability refers to the extent to which a particular ion can cross the membrane through a given ion channel. Neurons can change the permeability for a particular ion. This is also called gated ion channels. Ion pumps use energy to actively transport ions across the membrane against their concentration gradients. The process of neurons transmitting information starts when excitatory postsynaptic potentials (EPSPs) at synapses on the neuron’s dendrites cause ionic currents to flow in the volume of the cell body. Neuronal signalling can be...

Each sense collects, filers and amplifies information. Each system has specialized receptor cells that transduce the environmental stimulus into neural signals. The sensory nerves of the body travel up the spinal cord and enter the brain through the medulla and then go to the thalamus. After going through the thalamus, they travel to the primary sensory cortex and the secondary sensory cortex. Receptor cells share a few general properties:RangeEach sensory modality responds to a limited range of stimuli.AdaptationThis refers to how sensory systems stay fine-tuned. It’s the adjusting of the sensitivity of the sensory system to the current environment. AcuityThis is the ability to distinguish between different stimuli.Each level of processing (e.g: attention, memory, emotion) contributes to the end product of sensory stimulus. This leads to a subjective experience of sensory information. All senses pass through the thalamus before going to the appropriate sensory cortex. The nuclei in the thalamus are interconnected, which provides an opportunity for multisensory integration. Sound waves arriving at the ear enter the auditory canal. Here, the signals are amplified. It makes the eardrum vibrate and these vibrations travel through air-filled middle ear and rattle tiny bones which causes another membrane (oval window) to vibrate. The oval window is the door to the fluid-filled cochlea. There are tiny hair cells in the cochlea and these are the sensory receptors of the auditory system. The location of a hair cell determines its frequency tuning. The hair cells act as mechanoreceptors when deflected by the membrane, mechanically gated ion channels open in the cells allowing positively charged ions to flow into the cell. This will lead to depolarization and a release of a transmitter into a synapse between the hair cell and the nerve fibre.Axons from the cochlear and the olivary nuclei projects to the inferior colliculus where it can...

Cognitive control (executive function) allows us to use our perceptions, knowledge and goals to bias the selection of action and thoughts from a multitude of possibilities. It allows us to override automatic thoughts and behaviour and step out of the realm of habitual responses. It also allows us to plan for the future and troubleshoot problems. Cognitive control is essential for goal-oriented behaviour. The border between the frontal lobe and the parietal lobe is marked by the central sulcus. The most posterior part of the frontal lobe is the primary motor cortex. The unique cognitive abilities of humans may arise because of the prefrontal cortex and more because of how our brains are connected rather than due to an increase in the number of neurons. The prefrontal cortex is connected with other parts of the brain. The largest input comes from the thalamus. Almost all cortical and subcortical areas influence the prefrontal cortex. The prefrontal cortex consists of the lateral prefrontal cortex, frontal pole, medial frontal cortex and ventromedial prefrontal cortex.Dysfunction of the prefrontal cortex may result in perseveration, persisting in a response even after being told that it is incorrect. The patient may also be unable to understand the consequences of their actions. The deficits seem to be mild when the lesion is unilateral but severe when the lesion is bilateral. Dysfunction in the frontal cortex leads to a loss of goal-oriented behaviour. Patients show utilization behaviour, behaviour which an extreme dependency on prototypical responses for guiding behaviour.Goal-oriented actions are based on the assessment of an expected reward or value and the knowledge that there is a causal relationship between the action and the reward. A habit is an action that is no longer under the control of a reward but is stimulus-driven and automatic. Working memory is the transient representation of task-relevant information. It is the temporary...