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...

There is lateralization of sensory processing and motor output. The contralateral control of movement for the motor cortex is not absolute. Proximal muscle control is largely bilateral and distal muscle control is largely contralateral. The lateralization of language can be tested by using the WADA-test (temporarily anaesthetize left hemisphere). Lateralization of language can be left, right or bilateral. The following anatomical differences between the two hemispheres can be observed: a flatter Sylvian fissure on the left (1), difference in size in Heschl’s gyrus (2), difference in size in Planum Temporale (3), larger pyramidal cell bodies in the left Heschl’s gyrus (4) and more distance between patches in Wernicke’s area (5). Connections between cells are organized in patches. Anatomical differences do not correlate with language lateralization. Macroscopic and microscopic anatomical differences and functional differences exist between the two hemispheres, but are not absolute.The two hemispheres cooperate because the corpus callosum connects the two hemispheres, together with the anterior commissure and the posterior commissure. There is interhemispheric synchrony between neurons that respond to the same stimulus that activates cells with receptive fields in both hemifields. For split-brain patients, stimuli that are only presented to the right hemisphere cannot be verbally reported if there is a full split of the corpus callosum. When the posterior part of the callosum is sectioned, higher order, abstract information about the stimulus can be reported, but not the stimulus itself. Two hemispheres can search for a visual target independently if the corpus callosum is cut. Search time increases with half the slope of regular subjects when items are presented to two hemispheres simultaneously. There are differences between the left- and the right hemisphere. The right-hemisphere: is better at spatial and geometrical tasks (1), is...

Agnosias refer to failures of perception while the processes itself (e.g: the eye itself) is functioning normally. Visual agnosia refers to agnosia limited to the visual modality. There are four major concepts of object recognition: there is a difference between perceiving and recognizing (1), perception is of unified objects (2), perceptual abilities are flexible and robust (3) and the product of perception is interwoven with memory (4). The parahippocampal area and posterior parietal cortex process information about places and scenes. Output from the visual cortex is contained primarily in two major fibre bundles: fasciculi. The ventral (occipitotemporal) stream is the “what pathway” and the dorsal (occipitoparietal) stream is the “where pathway”. The what pathway is responsible for object perception and recognition and the where the pathway is responsible for spatial perception. There is also a what and where pathway for auditory stimuli. The pathways may carry similar information but they each support different aspects of cognition. Patients with optic ataxia can recognize objects but cannot use visual information to guide their actions. Saccades are quick eye movements. In patients with optic ataxia, saccades may be directed inappropriately. The two pathways are not isolated from each other but communicate extensively. Neurons in the parietal lobe have large, nonselective receptive fields that include cells representing both the fovea and the periphery. Neurons in the temporal lobe have large receptive fields that are more selective and always represent foveal information. There are three major subtypes of agnosia:Apperceptive agnosiaThis refers to a difficulty in recognizing objects from abnormal perspectives and is caused by a right-sided parietal lesion. Object recognition is limited when the perceptual input is limited. It can be seen as a problem with object constancy.Integrative agnosiaThis refers to an inability to...

The final common pathway of all motor output is the ventral horn in the spinal cord. The dorsolateral part of the ventral horn is involved in distal muscles and fine movements. The ventromedial part of the ventral horn is involved in proximal muscles and posture. Muscles make use of alpha neurons. It involves alpha neurons. There are different reflexes of the human body:Stretch reflex (posture)Activation of one muscle leads to the relaxation of the other muscle. The muscle spindle senses stretching, which activates the alpha motor neurons which leads to the muscle contracting.Golgi tendon reflex (protection from overload)Excessive weight on a muscle causes the neuron from the Golgi tendon to fire, inhibiting the motor neuron which leads to relaxation of the muscle.Withdrawal reflex (protection from damage)Activation of pain receptors on the skin causes the muscle to contract and withdraw.Crossed extensor reflexThe flexing of one muscle leads to the relaxation of another.The central pattern generator is the mechanism in the spinal cord that enables patterns (e.g., walking, breathing, swallowing) to be generated and is activated by a higher brain command or by proprioceptive feedback. Reflexes are processed and generated in the spinal cord. Reciprocal inhibition of antagonistic muscles refers to the relaxation of the flexor as the extensor contracts.Pyramidal tracts are axons that travel directly from the cortex to the spinal cord. The extrapyramidal tracts are axons that travel through another cortical structure to the spinal cord. There are several extrapyramidal tracts:Rubrospinal tractFrom the upper motor neurons in the red nuclei to the spinal cord. It controls muscle tone and distal limb muscles that perform more precise movements.Tectospinal tractFrom the upper motor neurons in the superior- and inferior colliculi to the spinal cord. It receives auditory and visual information and controls the orienting-response....

Emotions consist of a physiological response to the stimulus (1), a behavioural response (2) and a feeling (3). The function of emotions is activating the fight/flight response (1), making quick decisions based on emotional value (2) and anticipating the consequences of a decision (3) Basic emotions (anger, sadness, happiness, disgust, surprise, fear) are innate and universal emotions that correspond to facial expressions. Complex emotions are learned emotions, shaped by the culture and the environment. Emotions can differ on arousal (subjective intensity of emotion) and valence (positive/negative experience). Emotions are not traceable to specific brain regions.The James-Lange theory states that emotion has three components: cognition (1), readiness for action (2) and feeling (3). Emotion is a label to our responses. This theory is a flawed, as the autonomous nervous system is not differentiated enough to account for all emotions (1), hormonal feedback from the body is too slow to induce emotions (2) and hormone injections can cause different emotions (3).The hypothalamus is responsible for the readiness for action component of emotion. The sympathetic nervous system is involved in action. Cortical processing is involved in experiencing feelings. The anterior insula is involved in the awareness of bodily responses. The ventromedial prefrontal cortex is involved in using emotions for decision making. If the ventromedial prefrontal cortex is damaged, there is emotional perseverance (e.g., no fear extinction). The somatic marker theory states that the ventromedial prefrontal cortex starts an internal simulation to evaluate the emotional outcomes of decisions and these emotional outcomes (somatic markers) are used to guide decision making.The amygdala receives information from the entire brain and can influence the entire brain. It responds to emotional stimuli and neutral stimuli predicting motivating stimuli. It judges the emotional value...

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...